Dynaco PAS 3x Quad Cap and ticking sound

I got a PAS 3X and have been rebuilding it for the past couple of months. I've done it step by step so to speak so if I had any trouble I'd know where to look. I played music for about an hour after I replaced each part. Each test was fine but after replacing the Quad capacitor I now hear a ticking sound after about 10 - 15 seconds after powering on, so I turn it off. So far I have replaced (in order):

Selenium rectifier using 1N007 diodes, 2200uf 35V capacitors. (Radio Shack)

.1uf poly film capacitors for tone controls. (RS)

Power transformer PA 211 (Dynakitparts)

Quad capacitor, 10K and 47K resistors. The original is 30-20-20-10. The Dynakitparts replacement is 20-20-20-20.

***** ticking sound begins *****

.02uf 1K V ceramic disc capacitor on power switch.

PC-5 (Earhart Audio)

PC-6

***** ticking sound persists *****

I've done some re-soldering, I've triple-checked wiring and solder joints with a magnify glass. So, in my beginner audio repair mind it is the Quad cap although I doubt a new cap is bad. ??? I really want to fix this myself so any thoughts as to what the problem is or where I can find further assistance will be greatly appreciated.

jimmeq wrote:I got a PAS 3X and have been rebuilding it for the past couple of months. I've done it step by step so to speak so if I had any trouble I'd know where to look. I played music for about an hour after I replaced each part. Each test was fine but after replacing the Quad capacitor I now hear a ticking sound after about 10 - 15 seconds after powering on, so I turn it off.  So far I have replaced (in order):

Selenium rectifier using 1N007 diodes, 2200uf 35V capacitors. (Radio Shack)

.1uf poly film capacitors for tone controls. (RS)

Power transformer PA 211 (Dynakitparts)

Quad capacitor, 10K and 47K resistors. The original is 30-20-20-10. The Dynakitparts replacement is 20-20-20-20.

***** ticking sound begins *****

.02uf 1K V ceramic disc capacitor on power switch.

PC-5 (Earhart Audio)

PC-6

***** ticking sound persists *****

I've done some re-soldering, I've triple-checked wiring and solder joints with a magnify glass. So, in my beginner audio repair mind it is the Quad cap although I doubt a new cap is bad. ??? I really want to fix this myself so any thoughts as to what the problem is or where I can find further assistance will be greatly appreciated.

I am taking, from your description, that this is a physical tick from inside the unit, not an audio tick over the speakers.

If you are sure that the ticking is from the quad cap, and if it is a new cap, I have a few highly speculative options to suggest. But, first:
a) If you have access to a stethoscope, borrow one and verify that it is, in fact the cap. If no stethoscope, a length of soft tubing - one end in your ear, one end pointed at the suspect source.
b) Locate and verify the ticking source, as above.

If it is the cap, understand that reproduction quad caps as this one is, very likely, are not the same as they once were. They are, most likely, four separate caps concealed in the new cover, not a large, divided mass of foil, paper and gel as before. Normal heating and cooling may cause the group to 'click' as they expand and contract within the case.

It could also be the transformer heating up, as you will have increased the load on it (very slightly) via the silicon diodes and the lower capacity on the B+ supply.

I can also imagine a scenario where there is a capacitive discharge causing the clicking - but that would also be in the audio, not from the cap itself.

Try jumping a 20uF cap across each section of the new quad-cap, and see what happens. Being very careful.

jimmeq wrote:I got a PAS 3X and have been rebuilding it for the past couple of months. I've done it step by step so to speak so if I had any trouble I'd know where to look. I played music for about an hour after I replaced each part. Each test was fine but after replacing the Quad capacitor I now hear a ticking sound after about 10 - 15 seconds after powering on, so I turn it off.  So far I have replaced (in order):

Selenium rectifier using 1N007 diodes, 2200uf 35V capacitors. (Radio Shack)

.1uf poly film capacitors for tone controls. (RS)

Power transformer PA 211 (Dynakitparts)

Quad capacitor, 10K and 47K resistors. The original is 30-20-20-10. The Dynakitparts replacement is 20-20-20-20.

***** ticking sound begins *****

.02uf 1K V ceramic disc capacitor on power switch.

PC-5 (Earhart Audio)

PC-6

***** ticking sound persists *****

I've done some re-soldering, I've triple-checked wiring and solder joints with a magnify glass. So, in my beginner audio repair mind it is the Quad cap although I doubt a new cap is bad. ??? I really want to fix this myself so any thoughts as to what the problem is or where I can find further assistance will be greatly appreciated.

As it started after replacing the quad cap , i would reinstall the old quad cap. If the ticking stops i would return the quad cap.
Always nice to do one thing at a time. If it fails after a certain step, this step is suspected.

But why install a quad cap and replace Se when you can replace all of the power supply with a single board ?

peterh wrote:

As it started after replacing the quad cap , i would reinstall the old quad cap. If the ticking stops i would return the quad cap.
Always nice to do one thing at a time. If it fails after a certain step, this step is suspected.

But why install a quad cap and replace Se when you can replace all of the power supply with a single board ?

It would be nice to be sure that the ticking is a physical manifestation, and not audio.

Agreed on the single board concept. But he is where he is now.

First, thanks for the response, and my apologies for my questionable grammar and spelling errors. (Erhart) I broke off the twists on the old capacitor so reinstalling would be a challenge. The tick sound is physical; I have not tried to play the PAS while it is ticking. Seemingly after the rectifier tube warms up I hear a slight tick, tick...tick...tick....tickticktick....ticktick....tick.
I hear the randomly spaced tick sounds for maybe five seconds and then power off to avoid doing any damage.

I'll fashion a "stethoscope" over this weekend and isolate the tick sound on Tuesday. I'd like to resolve the tick sound first because it seems like the correct procedure. That said, since I will be adding the PAS to my collection I am not adverse to further modifications such as the power supply replacement.

jimmeq wrote:First, thanks for the response, and my apologies for my questionable grammar and spelling errors. (Erhart) I broke off the twists on the old capacitor so reinstalling would be a challenge. The tick sound is physical; I have not tried to play the PAS while it is ticking. Seemingly after the rectifier tube warms up I hear a slight tick, tick...tick...tick....tickticktick....ticktick....tick.
I hear the randomly spaced tick sounds for maybe five seconds and then power off to avoid doing any damage.

I'll fashion a "stethoscope" over this weekend and isolate the tick sound on Tuesday. I'd like to resolve the tick sound first because it seems like the correct procedure. That said, since I will be adding the PAS to my collection I am not adverse to further modifications such as the power supply replacement.

Remove the can cap, it's broken!
You have the option to reinstall the old one or wait for another cancap.

My apologies for some lack of information; I'm new to this. The tick does not occur at all with the rectifier tube removed. I removed it and powered on for 10 minutes and no tick is heard. (I'm using a stopwatch now.)

My procedure went as follows. A simple rolled paper tube was used as a stethoscope and the new can cap was the tick culprit. Although the twist lugs were almost gone, I was able to put the original can cap back in. No tick sound after 30 seconds!

Crap! After an estimated three minutes the tick returned just as bad as with the new can. The can cap was also very hot to the touch. (I don't know if this is normal.) With the can warm, the tick now begins after 20 seconds after power on.

I remembered it does not tick with the rectifier tube removed so I removed it and powered on. No tick whatsoever even after 10 minutes.

On a hunch my focus went to the rectifier tube socket. I noticed pin hole #1 was loose after jiggling each of  the wires to the socket. The other six pin holes were solid. I bent the lug end a bit and so far its been on 10 minutes and no tick. (Well, one tick after 12 min. And then I put pressure on #1 and it stops.) Does this make more sense that it's likely the loose socket pin holes?

At this point I think I will just get the power supply replacement from Erhard-Audio (Finally spelled correctly) and be done with it. I will also replace the tube socket with a new one and will post the results.

jimmeq wrote:My apologies for some lack of information; I'm new to this. The tick does not occur at all with the rectifier tube removed. I removed it and powered on for 10 minutes and no tick is heard. (I'm using a stopwatch now.)

My procedure went as follows. A simple rolled paper tube was used as a stethoscope and the new can cap was the tick culprit. Although the twist lugs were almost gone, I was able to put the original can cap back in. No tick sound after 30 seconds!

Crap! After an estimated three minutes the tick returned just as bad as with the new can. The can cap was also very hot to the touch. (I don't know if this is normal.) With the can warm, the tick now begins after 20 seconds after power on.

I remembered it does not tick with the rectifier tube removed so I removed it and powered on. No tick whatsoever even after 10 minutes.

On a hunch my focus went to the rectifier tube socket. I noticed pin hole #1 was loose after jiggling each of  the wires to the socket. The other six pin holes were solid. I bent the lug end a bit and so far its been on 10 minutes and no tick. (Well, one tick after 12 min. And then I put pressure on #1 and it stops.) Does this make more sense that it's likely the loose socket pin holes?

At this point I think I will just get the power supply replacement from Erhard-Audio (Finally spelled correctly) and be done with it. I will also replace the tube socket with a new one and will post the results.

Good!
ticking sounds like shorts in the cap, this will ruin your transformer!
That the ticking is gone when rectifier is out is clear as there is no B+.
Installing power supply board is a good choice. Don't use the amp until this is installed.

A few things on basic diagnostics - and please forgive the didactic tone.

a) Heat is bad - anything that gets unusually warm to the touch should be scrapped, replaced and/or repaired as appropriate instantly.
b) A dental pick is your best friend on new-to-you tube equipment. Before I even apply power, I will use tiny spiral brushes and contact cleaner (NOT DeOxit!) on all the pin sockets, then tighten them with the dental pick. Work from above and below.
c) Also - CLEAN and STRAIGHTEN the tube pins as well. I have an electric eraser from my college days and a lifetime supply of inserts. There are battery devices available today that do the trick as well. There is nothing like them to polish tube pins, contacts or other surfaces, leaving no conductive residue.
d) I will usually replace line-cords directly, even before any diagnostic efforts, with a polarized plug making sure that the "hot" side goes to the switch. I want the system *DEAD* when the switch is OFF.
e) Be patient, and be safe. Remember, somebody put this thing together in the first place, and, presumably, it worked then. Your job is repair-by-replacement, you are not inventing the wheel. You already know that it can be done - and likely without heroics.
f) YES, there are, occasionally, defective parts supplied to you by a vendor, and usually not by malicious intent. If something is not right, it is not necessarily your mistake. To the extent that you can screen parts prior to installation, it is a good idea to do so.
g) If you are removing a bad, defective, or otherwise undesirable part - TRASH IT IMMEDIATELY. Do NOT keep it around, worse, DO NOT, EVER, reinstall it.
h) To this end, taking lots of pictures through the process so as to have a ready reference to "before" is always a very, very good practice.

Usual stuff: Lethal voltages, cleanliness, good tools, good light, good ventilation - and so forth.

And: If this foray is not going to be a one-off, get an isolation transformer for your bench and work only from that during the restoration process. ONLY from that.

Enjoy, and best of luck to you!

A bsic question :
Is there any possibility that the rectifier is misconnected, puching out negative voltage to the
can-cap ? What voltage can be measured on the cancap when powered on ( for a short time ) ?
Is this voltage positive related to the chassies ?

peterh wrote:A bsic question :
Is there any possibility that the rectifier is misconnected, puching out negative voltage to the
can-cap ?   What voltage can be measured on the cancap when powered on ( for a short time ) ?
Is this voltage positive related to the chassies ?

I will say no because there was no real problems at all before I started replacing parts. I did check the wiring against the pictures in the manual and the builder did it correctly.

jimmeq wrote:

peterh wrote:A bsic question :
Is there any possibility that the rectifier is misconnected, puching out negative voltage to the
can-cap ?   What voltage can be measured on the cancap when powered on ( for a short time ) ?
Is this voltage positive related to the chassies ?

I will say no because there was no real problems at all before I started replacing parts. I did check the wiring against the pictures in the manual and the builder did it correctly.

What voltage is there om the can cap's first connection when powered on ?
Is it positive ?

This is getting way too complicated. If a multi-section cap is both warm and ticking, it is failing short, undersized (voltage) or it is grounding somewhere it should not. For the record, I am NOT a supporter of multi-section caps, new production or old. Do not multiply entities needlessly. Back in the day, they were considered to be an inexpensive means to save real-estate. Today, that is not a valid option given the relative size and quality of available caps.

Further, it is usually a good idea, when testing a pre-amp to have a signal source and power-amp immediately to-hand. I keep a small amp connected to a headphone box (2 x 5-watt, 100-ohm resistors in series with the jack) and a tuner on the bench. That and an eagle-eye on the ammeter, and if I hear anything untoward, I know a lot more than I would were the pre-amp bare.

I also keep a quantity of jumper wires (my goodness, but they are CHEAP - even for good ones!) such that I can breadboard parts before soldering - and verify that they are both doing their job and correctly installed.

After all this, and if you are correct that there are no induced failure points by your work, I would hazard a guess that the new quad-cap you have is defective. If you have even a VOM-based cap test function, the sections should all read the same, and somewhere within 20% of the actual rating. Too high (approaching/over 2x actual) and it is defective. Even 21% under, and it is defective. Also, look for shorts between the sections. Testing between any two sections should read approximately the total of the two. Draw it out so you understand.

Peter H has a good point. With the rectifier in place, what is the voltage at the first connection from the transformer to the multi-section cap? I would go so far as to suggest that you disconnect the transformer wire and test. If the cap is failing short (heat!!), it will draw down the voltage (and eventually damage the transformer). And if you have clips on your test leads, you can see if that voltage does drop when you touch the first cap section. CAREFULLY!

You're not kiddin'! I just wanted to replace some parts... I'm waiting to see my voltage tests appear here.

The original can cap is in and the voltages I measured all read as positive. Values in parentheses are from the manual.

Square = 630VDC   (405)
Triangle = 522VDC  (355)
Line = 452VDC (330)
Half-circle = 335VDC  (210)


12X4 PINS

1 = 616VAC (335)
6 = 307VAC (335)
7 = 633VDC (405)

These voltage reading seem awfully high to me.

Thank you all for your patience and guidance! I have just discovered that I have incorrectly wired the transformer. I mistakenly ran the red/yellow trans wire to pin #6 on the rectifier socket, and the red wire that should be on pin #6 is on the can cap lug ground. I will re-solder and send the results. Again thanks for the help!!!

It would be wise to replace the can cap in any case. How much internal damage was caused by the arcing? You have no way of knowing for sure.

Yes, the cap COULD still be fine - but after exposing it to voltages well above its rating and the arcing occurring I consider it suspect.

I made the corrections and all voltages are within tolerance. It appears I have mis-wired the selector switch to the PC6 board as I hear nothing from the FM/AM, FM-MPX or tape inputs. I do hear a slight tick from the speakers when I turn the L and R Treble controls past the center position so the PC5 board seems OK. I'm not concerned about this 'tick' at this point. I've matched the eyelet numbers on the PC6 board to the connections on the selector switch according to a wiring drawing I have and it looks correct. Obviously not though. This is a whole new issue and I'll ask for assistance from Erhard-Audio as he offers help with his boards. Although further input and advice is still welcome.

As for the original can cap...amazing! After correcting my wiring here's the voltage readings:

Square = 408
Triangle = 352
Line = 321
Half-circle = 200

After over 40 years and the abuse I put it through; still within tolerances. I've already ordered Erhard's drop in power supply replacement and after I fix the input issue I will be putting in the new power supply.

What a great learning experience this is! I'm taking the weekend off from the project and when I have news I will post. Thank you all!!!

You have replaced one ticking time bomb with another. Given all it has been through, I would be very, very careful of leaving the OEM quad-cap in place unsupervised. However, the Erhard unit will address all that...

Peter W. wrote:You have replaced one ticking time bomb with another.  Given all it has been through, I would be very, very careful of leaving the OEM quad-cap in place unsupervised. However, the Erhard unit will address all that...  

Yes. And thanks to the restored B+ ( 410V instead of 630V) that the new caps will survive.

I went over my wiring using the manual as a guide as if I were building the PAS from scratch. I found one loose wire, and added the connections for the 'mic' L/R. All other wires were correct and appeared well soldered. STILL...No sound. I thought for some reason if might be the Lepai Clss T amp, or my I phone connectin so I brought the PAS home and connected it to my (Known working) Samsung DVD-HD841 DVD/CD player and to a Sony STR-DH810 receiver as the power amp and I heard my Steve Davis CD playing! Sound! Music! Joy!
I thought for some reason if might be the Lepai Clss T amp, or my I phone I've been using to test for sound so I brought the PAS home and connected it to my (Known working) Samsung DVD-HD841 DVD/CD player and to a Sony STR-DH810 receiver as the power amp and I heard my Steve Davis CD playing! SOUND! Music! Joy!

After a few minutes I noticed the sound distorting worse and worse. I checked the tone controls, volume, and balance. 'POP!', and a little smoke bellowed from the new transformer! I unplugged it. Man, it was HOT! Weird because I had had it on for at least 30 minutes at the office while checking voltages; all of which were in spec which is why I thought she was ready to play.

My uneducated guess is all the stress on the transformer by being wired incorrectly and receiving over 600V. ???

The new power supply arrived just in time....and I'm foolish enough to assemble and put it in place. This has been challenging for this beginner. The best things are always after a hard ride... I will likely send it out to Erhard-Audio to do the tone controls, and go over all my work.

Guys and gals, the correct tools, and uses thereof, are important. They prevent disasters such as the above, or at least warn of their impending threats. And given the cost of the devices we are discussing, and the near-certainty that not all of us enjoy 6+ figure incomes (unless cents are counted) with 5+ figure discretionary incomes, investing in some basic tools is a wise move. That most of the tools will be otherwise useful as well only adds to that wisdom, and possibly enhances SO-approval.

1. A GOOD VOM. Something with cap measuring capacity, auto-ranging, and the ability to measure amps to a fine level. I keep a mid-range Fluke that accepts all sorts of different types of probes, and with some set-up, does measure up to ten (10) Amps. More than enough needed for around here. There are other brands, but few with the same resilience, warranty, utility and general excellent ergonomics.

https://www.amazon.com/Fluke-FLUKE-87-V-Digital-Multimeter/dp/B00T3LZLFG/ref=sr_1_3?ie=UTF8&qid=1539706339&sr=8-3&keywords=fluke+87+multimeter    

Spend Da Money!!

If one is going to do this for a hobby, a bench ISO-Variac with the correct metering is an absolute necessity, and will also save a great deal of heartache, paying for itself the first time a power or output transformer does not go up in smoke - both time and $$.

I keep this one (thanks, Bryan, for the use of the link):  http://www.byan-roper.org/steve/steve-at-play/antique-electronics-and-2/heathkit-ip-5220-variable.html   But, they were made by VIZ, RCA, and any of half-a-dozen other makers of equal utility. It will show tiny differences in load, and a transformer that gets hot will read as excess load well before any damage.

Spend Da Money.

We are all lucky - what with VTA creating new opportunities, and the fact that OEM Dynaco is so well supported such that parts are available. Not cheap, but available. But it is still incumbent on all of us to reduce our environmental footprint by not creating needless landfill for lack of the correct tools.

Minor rant to Rant (All in good fun!)

Yes, good tools make a big difference; I've been a DIY my entire life so far. "A craftsman does not blame his tools" so I'm not going too. I have an inexpensive VOM, and a cheap ESR meter. Decent Weller WP25 pen. I'm finding out if doing this is really for me so I didn't want to spend too much money on quality tools at first.

It was ME, the 'craftsman' that made the errors, not the tools. The high voltage was caused by me miswiring the transformer to the rectifier socket. I take full blame. I'm learning.

Replacing components seemed simple at first, and my miswiring caused too many headaches. I give myself credit for not attempting to restore my McIntosh C 28. I left that to SoundSmith. The PAS seemed like it would be pretty straight forward to restore. Nope. I also forgot to mention that I've assembled an ST-120 so I'm not just a rouge...

And now seriously, thank you for reading, and responding to my questions. And to stay on track.:

What are the thoughts on my destroying the brand new transformer. Too much high voltage?

jimmeq wrote:Minor rant to Rant (All in good fun!)

What are the thoughts on my destroying the brand new transformer. Too much high voltage?

Nope. Too much load. Something, somewhere, somehow, is shorted, partially at least. And why I ranted on a metered iso-variac. To be both didactic and pedantic (and, perhaps, just plain ick), one watt/hour = 3.412142 BTU/hr (1055 Joules). If that transformer is loaded a mere 7 watts over its proper rating - about the same as a vintage incandescent nightlight, not only will it be sizzling hot in a very short time, but it will fail not much later. You want something on your bench that will let you know if your device is above/at/below the load it should be drawing. And you should be able to observe those conditions over an extended period of time.

Yes, there are current-limiting devices, such as dim-bulb testers, but they are not fine enough to alert one to the typical 7-watt problem, for example.

We all make mistakes - some of us on a regular basis. What we want are means and methods to allow us to catch these mistakes before they cause a melt-down, or worse. To that end, nothing goes on my bench without a test on the Heath, and nothing comes off it without a several-hour burn-in on the Heath. Were I perfect, I could make do with a rusty screwdriver, a 200-watt soldering gun and a candle. As my level of perfection decreases, I need all the help I can get in my tooling.

Well, I reached the point where it is best to hand the PAS over to Erhard-Audio. It's been a learning experience. A big thank you to all who helped!