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    Please help me finish my PAS-2 upgrade

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    erhard-audio

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    Re: Please help me finish my PAS-2 upgrade

    Post by erhard-audio on Wed Dec 05, 2018 11:31 pm

    Bill,

    I just sent you a new 'pm'
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Thu Dec 06, 2018 10:21 am

    DynakitParts wrote:Bill,
         The 330-0-330 secondary voltage spec is based on full load. You measured 324-0-324 vac under no load. Figure about a 20 to 25 volt drop under full load.

    So...the high voltage secondary under no load should have been roughly 350-0-350 vac to 355-0-355 vac.

    The transformer appears to be defective. Why did they send you a dual voltage unit to begin with...did you request this?

    Kevin




    No, I didn't request a dual voltage transformer, but that's what they sent me.
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. on Thu Dec 06, 2018 2:53 pm

    Finally, I have to get off my fingers. I have resisted joining this thread until now as I observed much confusion and, together with much good advice, also advice that added (in my opinion) to the confusion.

    Starting out, I use a mid-end Fluke "True RMS" DVM with an 'analog' bar-graph to mimic a needle. Quite useful for showing 'dither'.

    There are a total of four (4) critical voltage points on the PAS. _all_ the others are quite flexible.  
    Voltages, generally, do not want to be more than 5% over.
    Voltages, generally, do not want to be more than 10% under.
    Take measurements at 120 VAC at the wallplate, as measured independently, with the unit ON. If necessary, use at least two (2) meters to verify the voltage.
    At 120 VAC, *both* primary windings should be in parallel. Otherwise, down-line voltages will be low. However, running them in parallel DOES NOT double the voltage, it does (very nearly) double the current produced. My preference is pretty much always leaning to dual-voltage transformers operating at the lower-of-two voltages for this reason.

    All voltages below with all tubes in place (loaded).

    The 12X4 is a 7-pin miniature. Clockwise, from the bottom 1 - 7.

    Pin 1 & Pin 6 to chassis:  335 VAC. Meaning that the actual as-measured may be:
    From: 351.75 to 301V.
    Pin 7 to chassis: 405 VDC. Meaning that the actual as-measured may be:
    From 425.25 to 364.5 VDC.

    DC Filament voltage wants to be from 11 V to 13.6 V. WARNING: Operating 9-pin miniature 12**7 tubes at/above 13.0 V WILL shorten their lives, considerably. Below 10.8 V may lead to lazy cathode syndrome, but that is MAY, not WILL. But, that range is still within parameters.
    AC filament voltage (pins 3&4 on the 12X4 may be from 10 V to a full 12 V.

    All the other voltage processing is done on the boards or by the Quad-Cap RC array. What is key are the input voltages.

    What is coming from the transformer secondaries is within parameters - albeit at the margins.
    Voltages after that are not. Full stop.

    One of the reasons I stayed away is that diagnosis (and suggestions) at-a-distance is fraught with difficulties, and a simple turn-of-phrase may lead to a poor or damaging result. Things I take for granted, and directions given based on such my become misdirected. But despite all that, here goes:

    Bill:

    Put everything aside and out of sight-and-mind for 48 hours.
    I will assume you are retaining the 12X4
    On the new cap-board, REMOVE ALL WIRES. Reconnect in this order:
    Indicator lamp wires (black-black) to CN2A #1 and CN2 #2
    Blue-Blue filament winding wires from transformer to CN2A #2 and CN2 #1
    Red-Red B+ Winding wires to CN1 #2 & CN1 #3.
    Connect the wire at Pin 7 of the 12X4 to CN1 #1

    Install a ground-lug under the chassis with either a KEP-nut or lock-washer on the front-most transformer bolt. THAT will be your common ground from the transformer, and from the PCBs, and from the new cap board (AKA "Star" ground).

    Take a twisted-pair from the ground points on the cap-board to the new lug.

    Now test for voltages (to the chassis) at CN 3 & 4. And report back. No load on the board.

    We will go on from there.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Fri Dec 07, 2018 6:45 am

    Hi Peter.  I'm glad that you have been following this. I fully understand what you say about the perils of misunderstanding at a distance and the possibility of resulting damage to equipment or to health.  High voltages can be nasty when not respected.

    I am retaining the 12X4.

    In a reply (when the cap board seller was still responding to my mails, which is no longer the case), he wrote:

    "1. Better use a DMM to check the transformer output voltage of the RED pair and the BLUE pair of wires first" (by 'first' he means "before connecting the transformer leads to the board and to the 12X4")

    "2. If the BLUE pair output voltage is 10.5V AC, then correct them to CN2 & CN2A at the cap board."

    "3. IF the RED pair output voltage is 335V AC , then one RED wire should connect to 12X4 pin 1 and the other RED wire should connect to 12X4 pin 6. The DC output of 12X4 pin 7 should be connected to CN1 -12x4 on the cap board."

    "4. Don't connect the RED wires to CN1 - RED RED on the cap board.  CN1 RED RED is for testing only."
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sat Dec 08, 2018 3:35 pm

    It's only #4 above that concerns me.  I don't understand why "Red" is even written on the cap board at CN1, given that "Blue" is written at CN2 and at CN2A, and that is indeed where the blue transformer wires are to be connected.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Sat Dec 08, 2018 5:47 pm

    billinrio wrote:It's only #4 above that concerns me.  I don't understand why "Red" is even written on the cap board at CN1, given that "Blue" is written at CN2 and at CN2A, and that is indeed where the blue transformer wires are to be connected.

    billinrio wrote: ...
    In a reply (when the cap board seller was still responding to my mails, which is no longer the case), he wrote:
    ...
    "4.  ... CN1 RED RED is for testing only."

    PeterCapo wrote:Looks like the board has the option of replacing the 12X4 with solid state diodes (D1 and D2 in the cap board schematic), but your photo does not show such diodes in place (not to be confused with the other two diodes for the filament supply).

    If you have a look at the schematic and at the cap board itself, you will see that the connection points on the cap board ostensibly for the two red leads are adjacent to [what appear to be] silk-screened symbols for two solid state diodes that are not actually installed on the board.  This may have been part of an exploratory effort to offer the option of replacing the 12X4 with solid state diodes, an effort that may not have been fully developed, at least in terms of their documentation.

    If you connect the two red leads to the board as it is now, they will be at open circuit as you apparently had them in Post n°12:
    billinrio wrote: ... But measuring the tube pin voltages shows 0V in the case for pin 1 on all the tubes.

    By the way, if you plan to take readings at the outputs of the cap board (CN4 terminals) with their wires disconnected (unloaded outputs), you might exceed the voltage ratings of the capacitors (on the cap board).  This is, of course, provided the input to the cap board is actually connected.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 09, 2018 8:04 am

    Thanks for your explanation.  
    My quoting of point No.4 of the cap board seller's instructions: "Don't connect the RED wires to CN1 - RED RED on the cap board.  CN1 RED RED is for testing only" was really due to the fact that in Post #78 that's precisely what I am instructed to do.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Sun Dec 09, 2018 2:54 pm

    It's a long thread, and it would be easy to miss details.

    So, some thoughts regarding the tolerances in the voltage readings... here is an excerpt from the Dynaco PAS 2 manual, page 15: "Deviation of greater than 20% of these voltages may be an indication of malfunctioning; although deviations as high as 50% will not cause complete lack of sound."

    Again, when I reworked my PAS, my voltages were close to the standard values in the chart.  While I don’t want to be too dogmatic about this, I would think that if the voltage readings are not close to the reference values, then the PAS is not performing at its full potential.  That’s our goal here: to get closer to, and to enjoy, the potential of the original PAS circuit and not have it just limping along.

    If we accept wide deviations of the voltage readings, then you’re done right now – nothing more for you to do, just hook it into your system and use it, as Dynaco said deviations as high as 50% will not cause complete lack of sound.

    But, if anyone can get your voltages to line up closely with the chart without a new power transformer, and without using nonstandard component values or making other changes to the circuit, I’m all ears.


    Last edited by PeterCapo on Sun Dec 09, 2018 3:17 pm; edited 2 times in total (Reason for editing : Add idea.)
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 09, 2018 3:15 pm

    PeterCapo wrote:It's a long thread, and it would be easy to miss details ...

    But, if anyone can get your voltages to line up closely with the chart without a new power transformer, and without using nonstandard component values or making other changes to the circuit, I’m all ears.

    I am all ears as well.

    I'm wary about accepting wide deviations of voltage and  just hooking the preamp as it is into my system and seeing what happens.  I wouldn't be satisfied  merely by the fact of not having a complete lack of sound. My goal, of course, if for the preamp to perform optimally.

    I contacted Triode and they replied three days ago, "I will pass this on to your tech and of course, we will back up the transformer if it is defective.
    Thank you,
    Jan"

    I'm not sure what "back up" means, especially because they delivered the transformer to me when I was at a U.S. address, and now we have to deal
    with expensive international mail rates for (if they so require) my returning the transformer to them, and then (if they agree that it is indeed defective) shipping me another one.  The cost of shipping the transformer to them and then for me to receive one back from them would be at least, and probably more than the original cost of the transformer itself.


    Last edited by billinrio on Sun Dec 09, 2018 7:10 pm; edited 1 time in total
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Sun Dec 09, 2018 4:34 pm

    I'd be concerned that another transformer from Triode might have a similar problem.  I know dynakitparts.com makes quality stuff.  Especially after all this, I'd personally want to go with the dynakitparts transformer, but, of course, it's your call.

    While you are waiting on resolving the power transformer, you could still check out some other things.  While I think it would be preferable to have a power transformer that is performing really well, you could still have other issues even with a perfect transformer (if there were such a thing).  A new transformer cannot do anything to help miswiring, incorrect component values, defective parts, etc.  In particular, your last voltage readings at PC5 tube socket pins 1 were about 35% low.  Not sure the transformer can explain a discrepancy as large as this.

    Here are a few things to check:

    1. Please correct me if I have it wrong, but I believe Peter W. was suggesting removing the wires from CN4-1 and CN4-2 and then taking the unloaded voltage readings at each one (and the same for the filaments at the CN3 outputs).  In taking the unloaded readings, it would be prudent to monitor the voltage across the capacitors on the cap board while slowly increasing the variac.  Two hurdles.  First, you'd need to know the voltage ratings of all six capacitors, and hopefully they are marked in a readable format and not in some kind of cryptic part# coding.  You'd also need to know where to measure the voltages across them, which could get confusing.

    2. Peter W. also suggested rechecking the wiring to the cap board, which is always a good idea.

    3. You could also have a look back at Post n°54, which is what I had in mind before the transformer took center stage.  

    3.5 As we have suggested, verifying readings with a second meter would be a really good idea.

    4. One other thought for now...  When you took the unloaded readings of the two red wires of the power transformer, you said that you left the red-yellow center tap wire connected to your chassis ground point, is that correct?  You'd just want to make sure that while one lead of the meter was on each red wire in turn that the other meter lead would directly contact the red-yellow wire.  To eliminate any doubt, you could try removing the red-yellow wire from the ground point and make the measurement directly between each red wire in turn and the disconnected red-yellow center tap wire.  Hope that makes sense.

    5. I believe Peter W. was also suggesting revisiting/shoring up your ground point.  If you don't have a proper ground, it could cause problems.

    Hope we will get some more input from others.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Sun Dec 09, 2018 9:07 pm

    Your schematic in Post n°8 shows C1 through C6 rated for 450 VDC apiece.  It shows C7 and C8 rated for 25 VDC apiece.  Just the same, try to visually confirm the markings right on the parts themselves.  After all, they had an incorrect value resistor in the board.

    Disconnect the wires at CN4-1, CN4-2, CN3-1, CN3-2, CN3A-1, CN3A-2.  Monitor the following while gradually increasing the variac to a measured 120 VAC (stop if you reach the voltage rating on any of the capacitors and please note the variac output at that point):

    Monitor the voltage across C1: one meter lead on CN1-1 and the other lead to ground.
    Monitor the voltage across C2: one meter lead on the junction of the 47K resistor and the two 10K resistors and the other lead to ground.
    Monitor the voltage across C3 and C5: one meter lead on CN4-1 and the other lead to ground.
    Monitor the voltage across C4 and C6: one meter lead on CN4-2 and the other lead to ground.
    Monitor the voltage across C7: one meter lead on CN3-1 and the other lead on CN2A-1.
    Monitor the voltage across C8: one meter lead on CN2A-1 and the other lead on CN3A-1.

    Of course, this is being extra thorough.  All things being equal, you should only need to monitor the voltages at the outputs and not every node along the way.  But, given the question marks hanging over this project, let's look at it in detail and see if it yields any clues.

    If you can reach 120 VAC from the variac without exceeding the ratings of any of the capacitors, please report the readings at CN4-1, CN4-2, CN3-1, CN3-2, CN3A-1, and CN3A-2.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio Yesterday at 6:26 am

    PeterCapo wrote:I'd be concerned that another transformer from Triode might have a similar problem.  I know dynakitparts.com makes quality stuff.  Especially after all this, I'd personally want to go with the dynakitparts transformer, but, of course, it's your call.

    While you are waiting on resolving the power transformer, you could still check out some other things.  While I think it would be preferable to have a power transformer that is performing really well, you could still have other issues even with a perfect transformer (if there were such a thing).  A new transformer cannot do anything to help miswiring, incorrect component values, defective parts, etc.  In particular, your last voltage readings at PC5 tube socket pins 1 were about 35% low.  Not sure the transformer can explain a discrepancy as large as this.

    Here are a few things to check:

    1. Please correct me if I have it wrong, but I believe Peter W. was suggesting removing the wires from CN4-1 and CN4-2 and then taking the unloaded voltage readings at each one (and the same for the filaments at the CN3 outputs).  In taking the unloaded readings, it would be prudent to monitor the voltage across the capacitors on the cap board while slowly increasing the variac.  Two hurdles.  First, you'd need to know the voltage ratings of all six capacitors, and hopefully they are marked in a readable format and not in some kind of cryptic part# coding.  You'd also need to know where to measure the voltages across them, which could get confusing.

    2. Peter W. also suggested rechecking the wiring to the cap board, which is always a good idea.

    3. You could also have a look back at Post n°54, which is what I had in mind before the transformer took center stage.  

    3.5 As we have suggested, verifying readings with a second meter would be a really good idea.

    4. One other thought for now...  When you took the unloaded readings of the two red wires of the power transformer, you said that you left the red-yellow center tap wire connected to your chassis ground point, is that correct?  You'd just want to make sure that while one lead of the meter was on each red wire in turn that the other meter lead would directly contact the red-yellow wire.  To eliminate any doubt, you could try removing the red-yellow wire from the ground point and make the measurement directly between each red wire in turn and the disconnected red-yellow center tap wire.  Hope that makes sense.

    5. I believe Peter W. was also suggesting revisiting/shoring up your ground point.  If you don't have a proper ground, it could cause problems.

    Hope we will get some more input from others.

    Here are some photos of the caps on the board:



    And this is my "second meter" (no joke). So, I really can't rely on it.  I would love to have a Fluke, but ....



    I've created a single chassis ground connection:
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio Yesterday at 10:41 am

    Here are the capacitor measurements, all at 120VAC.
    Voltage across C1: one meter lead on CN1-1 and the other to ground: 442V
    Voltage across C2: one meter lead on the junction of the 47K resistor and the two 10K resistors and the other lead to ground: 434V
    Voltage across C3 and C5:one meter lead on CN4-1 and the other to ground:412V
    Voltage across C4 and C6:one meter lead on CN4-2 and the other lead to ground:425V
    Voltage across C7: one meter lead on CN3-1 and the other lead on CN2A-1: 16.3V
    Voltage across C8: one meter lead on CN2A-1 and the other lead on CN3A-1: 16.3V[/b]


    When you day, "please report the readings at CN4-1, CN4-2, CN3-1, CN3-2, CN3A-1, and CN3A-2".
    Are the readings with the wires still removed from these points, or with the wires reconnected?


    Last edited by billinrio on Mon Dec 10, 2018 11:15 am; edited 1 time in total
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 11:14 am

    I'd like to know what Peter W. thinks about those readings...
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. Yesterday at 11:31 am

    PeterCapo wrote:I'd like to know what Peter W. thinks about those readings...

    They are all massively too high. From which I may draw only three (3) conclusions - and these I will list in rank order of likelihood in my mind:

    a) The measuring meter(s) is(are) defective.
    b) The cap board is defective.
    c) The new transformer is defective.

    The first set of readings was (apparently) too low.
    The next set of readings is too high. Wish I was there.

    At 120 VAC at the wallplate, the reading on the filament winding should be somewhere around 11 VAC under load!

    Bill:

    Please adjust your Variac until the reading on the filament wires (blue/blue) when connected to the 12X4 reads 11 VAC. Then recheck the other readings. Please let us know.

    Thanks!
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 11:36 am

    But they are unloaded.  Shouldn't they be higher than when loaded?

    If they are way too high, as you say, how do we account for one of the nodes on PC5 being 35% low? And the unloaded output from the transformer being low?  This whole thing has been a portrait in contradictions.
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. Yesterday at 11:45 am

    PeterCapo wrote:But they are unloaded.  Shouldn't they be higher than when loaded?

    If they are way too high, how do we account for one of the nodes on PC5 being 35% low? And te unloaded output from the transformer being low?  This whole thing has been a portrait in contradictions.

    Exactly that. And the common denominator to a large series of conflicting readings is the meters being used to do them.

    Once upon a time, I had a Hickok tube tester with a failing 83 in it. Plenty of current for a low-signal tube, not enough for a power pentode, or even a 2A3. That is how I learned a  hard lesson on calibrating and testing test-equipment prior to any sort of potentially serious (costly) diagnosis.

    I am guessing that ten minutes on either of our benches would get to the bottom of this. But diagnosis-at-a-distance is difficult, even with experts on either end.

    But-for the filament winding, I would like readings to the chassis, (ground), not to another point on the cab board.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 12:01 pm

    Or, perhaps, something in the applied technique - no offense, Bill, but it's near impossible to connect the dots here. As I had mentioned in a prior post, some meters have a zeroing feature that should be done before taking readings, although that is more for resistance readings - but have you looked up this possibility in the manual for your meter? Or, the meter might be out of calibration or otherwise flaky.

    So... thought experiment time. Let's just say the figures have been correct (even though they are in doubt). I don't have a reference for what the cap board's figures should be, unloaded. Maybe they would be even higher with a different power transformer, I don't know. If so, it still leaves us with the possibility that the power transformer's HV is running low. But, I am still not sure this accounts for the readings on the PC boards.

    Bill, let's revisit the resistors on the cap board. Can you post a photo showing the resistors, one at a time if need be, along with their respective silk-screened markings, R1, R2 and R3? I just want to verify the right values are in the right places, though I am kind of grasping at straws... please let us know.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 12:03 pm

    Is the meter showing a low battery indicator, by any chance?
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio Yesterday at 12:37 pm

    The meter (a Wavetek DM5XL) has a fresh 9v battery. I've looked through the manual. It doesn't have a calibration feature.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 12:49 pm

    Bill:

    On PC5, please verify the value of the resistor directly off of pins 1 and pins 3 of both tube sockets (four resistors, total).  Please quote the color bands on each one.  Close up photo would also help.

    Please also post the image of the resistors on the cap board so that the silk-screened designations are visible, R1, R2 and R3.


    Last edited by PeterCapo on Mon Dec 10, 2018 1:00 pm; edited 1 time in total
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 12:58 pm

    Peter W. wrote:Bill:

    Please adjust your Variac until the reading on the filament wires (blue/blue) when connected to the 12X4 reads 11 VAC. Then recheck the other readings. Please let us know.

    Thanks!

    With 120 VAC on the primary, his Triode USA PT specs at 12 volts loaded, vs. 11 volts for the original transformer, by the way.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio Yesterday at 1:25 pm

    Peter W. wrote:
    PeterCapo wrote:I'd like to know what Peter W. thinks about those readings...

    Bill:

    Please adjust your Variac until the reading on the filament wires (blue/blue) when connected to the 12X4 reads 11 VAC. Then recheck the other readings. Please let us know.

    Thanks!

    Umm.... there are no blue/blue wires connected to the 12X4. Do you mean the heater supply wires that go to CN2A-2 and CN2-1?
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo Yesterday at 1:37 pm

    I think he meant for you to measure the filament supply output with the cap board loaded again. The Triode PT specs at 12 volts for the filaments with 120 VAC mains. Your readings unloaded were much higher.

    Look, I think we have to distinguish between loaded and unloaded figures. The unloaded figures will be higher than loaded figures, but we don't have specs for what unloaded B+ and filaments should actually measure.

    At this point, I am in favor of:
    1) going to whatever lengths necessary to verify the values and proper locations of the three resistors on the cap board and also the resistors on PC5 that I asked about in Post n°96
    2) review the ground connections
    3) if 1 & 2 above seem okay, then I vote for a new dynakitparts power transformer

    That's it. If anyone else has any other ideas, please speak up.
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. Yesterday at 2:22 pm

    PeterCapo wrote:I think he meant for you to measure the filament supply output with the cap board loaded again.  The Triode PT specs at 12 volts for the filaments with 120 VAC mains.  Your readings unloaded were much higher.

    Look, I think we have to distinguish between loaded and unloaded figures.  The unloaded figures will be higher than loaded figures, but we don't have specs for what unloaded B+ and filaments should actually measure.

    At this point, I am in favor of:
    1) going to whatever lengths necessary to verify the values and proper locations of the three resistors on the cap board and also the resistors on PC5 that I asked about in Post n°96
    2) review the ground connections
    3) if 1 & 2 above seem okay, then I vote for a new dynakitparts power transformer

    That's it.  If anyone else has any other ideas, please speak up.

    WARNING: I am casting back to my dim-and-distant memory of Ohm's Law and the nature of rectifiers on this one. And, deriving from the OEM design. So I may be WAY off, but it does pencil.

    a) OEM uses a Full-Wave rectifier (NOT a bridge) across two selenium diodes, each one dropping about 1 volt in that configuration.
    b) The DC load on the filament supply is 1.2 A (150 ma x 8 )
    c) The AC load on the filament Winding is 300 ma.
    d) The theoretical voltage output from the transformer should be, unloaded, theoretically, again, about 12 AC volts. Theoretically, rectification (full wave) takes that to about 14.8 volts. The selenium diodes drop that back to about 12.8 VDC.
    e) Assign a resistance of 200 ohms (in series/parallel) net to the four tubes.
    f) Assign a 1-ohm forward-resistance to a silicon diode. It will be a little less.


    This calculates to 11.47 VDC, loaded.

    So, from this very rough calculation  - the voltage on the filament supply winding (unloaded) should be about 12 VAC. Or slightly higher as we have not factored the 12X4 300 MA current draw as a separate number.

    Loaded, the output from the filament supply should be ~11.5 VDC To the chassis. Unloaded (no tubes but the 12X4), it should be around 12.8 VDC to the chassis.

    I am functioning on the assumption that the Cap Board is meant to duplicate the voltages of the OEM supply, both filament and B+.
    I am functioning on the assumption that the new transformer has two (2) primary windings, and that they are connected in parallel.

    I want to get past the filament voltages before delving into the B+. If we do, we have at least one successful diagnosis.

    NOTE and FOR THE RECORD: I was a Fine Arts/Architecture undergraduate major. And although I took multiple engineering courses towards an MS, nothing in EE. My electrical knowledge is based on working my way through schools with the tools - not from a classroom.

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    Re: Please help me finish my PAS-2 upgrade

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      Current date/time is Tue Dec 11, 2018 8:44 am