Please help me finish my PAS-2 upgrade

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Thanks for the "graphic" description of  the problems/dangers with unsoldering radial caps.

I would be very willing to send it to someone to work on it, but that would mean shipping it internationally. And that's out, since the freight alone would come to more than the preamp is worth.
I can find no qualified techs here.  I live in a city with a population of 1.5 million, and I can bet that mine is the only Dynaco equipment in town.  When I Google "Dynaco repair / restoration" (in Portuguese, of course), I get no hits from anywhere in the country.  The Brazilian equivalent to eBay is called "MercadoLivre".  A search there for "Dynaco" gives me just one hit  - some guy a thousand miles from here trying to unload a Stereo 120 for $600.  So, I'm not going to get any local help to narrow this problem down.

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First of all, I want to thank you sincerely for your patience and your time spent on this thread. You are a generous guy, and make me feel that you "have my back" and thus a bit less isolated here with this problem.
I have lots of tube equipment, including a pair of factory Dynaco MKIV's, and a pair of Heathkit W5M's (with the Peerless 16458 transformers) that I've collected beginning with my teenage years in the U.S. While I was there, it was always easy to buy tubes, quality caps and resistors, and whatever I needed to keep the equipment functioning.  My soldering skills are quite adequate, I think, and I have a good soldering station that allows me to control the temperature of the tip. I use desoldering wick, brought from abroad, of which I have a good supply. My meter is a simple one - a Wavetek DM5XL. I no longer have its manual, lost somewhere during various international moves, and I've searched for, but haven't found a copy on the internet.
I speak, read, and write a number of languages (I'm a linguist), but schematics are in a "language" that I've never mastered, and I much admire those who understand them (can one begin to learn this at 75?)
I will pursue verifying the values of the resistors off of pins 1 for both tubes on PC5, and see what I might discover.

Billinrio,
            I have been following all these Posts and I must commend Peter for his continued efforts to help a fellow member. This is what this Forum is all about.
Anyway...do not overlook the possibility that the power transformer is the culprit. If you can...Measure all the secondary voltages of this power transformer under "No Load"
with your line voltage set a 120 vac. Let us know what you measure.

Regards....Kevin

DynakitParts wrote:Billinrio,
            I have been following all these Posts and I must commend Peter for his continued efforts to help a fellow member. This is what this Forum is all about.
Anyway...do not overlook the possibility that the power transformer is the culprit. If you can...Measure all the secondary voltages of this power transformer under "No Load"
with your line voltage set a 120 vac. Let us know what you measure.

Regards....Kevin

Thanks Kevin.  I'll check the transformer.  I just assumed that since it's new, it's good, and thought that this was confirmed by the fact that that all of the 12X4 pinouts are correct.
What are the "secondary voltages" compared to what, I guess, would be "primary voltages?  
I assume that by "under no load" you mean that I should take the transformer's ouput leads out of the circuit.

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For my transformer (http://www.triodestore.com/pa522.html), then, I should de-solder the red leads from pins 1 and 6 of the 12X4, and remove the two blue transformer leads from the cap board.  I assume that the transformer's ground wire (red/orange) can remain connected to the preamp.  Then, having powered up the preamp at 120VAC, I will measure the VAC voltage from each red wire to ground, (which should be 330VAC) and the VDC of each transformer blue lead to ground (which should be 12 VDC).  For the meter, I'll use cables with alligator clips on the probe ends, which seems to me safer than trying to touch the transformer's wires with a needle probe.

I believe you can just remove the rectifier tube, and all the other tubes on PC-5 & PC-6 plus the pilot lamp to reduce he current load as opposed to de-soldering any leads for you to take these measurements. I do not have a PAS unit in here to confirm this (I'm out of the office) but I believe this to be correct.

Kevin

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I received Kevin's message after I had already unsoldered the to leads to the 12X4. At 120VAC measured out of the variac, I read 324VAC at both of those leads. I will now solder them back to the 12X4. How is the voltage from the blue transformer leads measured?

Peter,
I would expect all the secondary voltages to be much higher with the tubes removed but you are correct about the charging of the electrolytics. I just wanted to make this an easy task for Bill to measure these voltages. I'm suspect of the Triode power transformer....as I'm suspect of anything these guys now currently sell. I will say no more but you most likely know what I mean.

Kevin

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May I call you Bill?
                           Voltage readings on the high voltage secondary's should be about 345 vac (Red to Red/Yellow) no load volts.... full load volts should measure about 330 vac.

Measure the filament voltage across both Blue Leads....no load volts should be about 12 vac.....full load volts about 10.9 vac

Keep in mind that our PA 211 transformer was wound to closely match the secondary voltages of the original Dynaco PA 211 at 120 vac. We did some comparison testing of Triode's version and found it to be also quite close to the original voltage specs but the current rating of this unit was a bit low @ 800 mA. We raised this on our PA-211 version to 1.25 A which allowed this unit to run somewhat cooler than the original. I have some data in support of this somewhere in the archives.

Anyway...It appears to me that the secondary (NLV) voltages are about 20 volts too low...Defective transformer?

Kevin

Of course you can. All of my friends call me Bill (although in Brazil it comes out "Be-uw" ( at the end of words,Portuguese doesn't have our "L" sound with the tongue touching on the front of the palate).

I've already re-connected the red transformer wires to pins 1 & 6 of the rectifier tube.
I measured 324VAC from the unsoldered red leads to ground. Should I have involved the red/yellow transformer ground lead?

Measuring the filament voltage across the Blue transformer leads, I get 11.7 vac with a 120vac input.

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Yes, Peter, I did leave the yellow-red transformer lead connected to ground on the chassis.  And I did measure each read lead to ground, and got that 324vac result for each.
It's very disappointing to discover that a new component that I purchased from what I thought was a reliable source, is defective.  I don't know whether Triode backs up their products with any kind of guarantee. I purchased the transformer, and the cap board, and the new PC boards, when I was in Portland OR in April visiting family. It's only now that I have been able to be back in Brazil with access to my PAS2 that I have tried to install the transformer with the results we know. Not being in the U.S. makes everything a bit complicated.

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Bill,
It's now more than (6) months since Triode sold you this transformer. I doubt you will be getting anything back from them although if you made this purchase with a credit card you may have some recourse as Peter suggested. Good luck.

Email me if you decide to purchase a replacement transformer. Another option would be to purchase a regulated power supply from Erhard Audio.

Best regards,

Kevin

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Peter,
When in doubt....read the instructions....you are correct. I trust Bill is still following all of this?

Kevin

DynakitParts wrote:Bill,
     It's now more than (6) months since Triode sold you this transformer. I doubt you will be getting anything back from them although if you made this purchase with a credit card you may have some recourse as Peter suggested. Good luck.

Email me if you decide to purchase a replacement transformer. Another option would be to purchase a regulated power supply from Erhard Audio.  

Best regards,

Kevin

According to the description of the transformer on the Triode USA site (http://www.triodeelectronics.com/pa522.html)
"Secondary is 330-0-330VAC at 15 ma DC rectified current, plus 12V at 800ma for filaments & pilot lamp. Primary is dual 120/240VAC 50/60 Hz."
Are my measurements far from these specs?

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

PeterCapo wrote:I just read the description on the Erhard Audio webpage, and if I correctly understood, his regulated supply won't work with the original PC5 and 6 circuits?  http://www.erhard-audio.com/Power_Supply_Kits.html

that is correct. The original Dynaco filament supply for the PC6 has one end tied to ground. The regulated DC filament power supply will not work with one end of the filaments tied to ground. It could work, but one would need to mod the pcb, cut tracks...too messy.