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Critical Errors of a Rookie, Dynakit Pas 2

zenarrrow

zenarrrow

Well-Known Member
So long story short, I have a Pas 2 that goes to my ST-70 I bought it like 2 years ago. I maybe have put like 5 hours on it as the sound has always been "tinny" very fatiguing to listen to.

So I have been reading a bunch of threads on it and decided I would start by replacing both the PCB 5 and the PCB 6 with already stuffed boards. I did that today it now still powers up, but only the Right channel is working on the Phono stage, I tried plugging my reel to reel in and get nothing from either channel on it.
 
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Ya broke it! :D

It has to be something you did as it worked before you started replacing parts. Double check your soldering and connections.
 
cademan said:
Ya broke it! :D

It has to be something you did as it worked before you started replacing parts. Double check your soldering and connections.
Click to expand...

Will do first thing in the morning, as I have all my equipment at work. Good place to start, thanks for the reply.
 
Strangest thing, when I turn off my pas before it fades out the left channel kicks in for a few seconds, and then if I start it in the beginning the left works for a few seconds.
 
I was thinking, when I swapped boards I exchanged wire for wire. Somega wires were barely long enough and I had to make them stretch in order to get them ro make the connection. Should I replace the super short ones, to make sure I am getting a good connection?

For some reason I don't get much love around here, don't know why. But I would love to have this pas running smoothly. Maybe I will have to do my best and try and piece together all the threads I have been reading. Hopefully I can get 'er running properly. Thanks, Joe
 
Does your multimeter have a continuity beeper for checking diodes? You can use that to check the selector switch and any other circuit for opens. Like a poor man's signal tracer. Clip one lead to the center of the right phono Rca, set switch to that input and touch the signal input wire on the phono board. If it beeps you likely have any good enough connection. Check each input this way to verify the switch. The selector can be any major source of lost music on these in my experience.
 
Do you know for certain the new boards work? Might not be you at all. Yes, I'd lengthen my shorts.
 
i was thinking the tube goes into saturation from a defective component.

Is this a problem only on the phono side or do the line level inputs have the same issue? Not quite clear if the line stage is dead on both sides or what. If the line stage is dead on both sides, the phono should be too so I'm confused by your symptoms here.
 
So this is what I have found thus far. Mind I have no way to test this as I am away from my home stereo. But I am able to work on my pas 2. So a test will be done tonight.

First thing I checked my soldering. Right off on the PCB 5 I found the #1 hole that holds a short black wire to the vol pot and a London black wire to the out put rca jacks on top and then on the bottom 1 brown wire that goes to the aluminum can (filter?). I noticed the top soldering was shabby and in fact the line going to the rca jacks was indeed loose. So I took my time and got all 3 wires securely in there and did a much better soldering job.

I then went through the entire PCB 5 and desoldered all the connections on the board and made double sure they were in the sockets good before I soldered them, again making sure to get a good solder on both sides of the board so that everything is plenty secure.

Looking at the black line that runs to the output jacks, this is probably why I was getting no tape or line stage power to the output?

Also, I noticed yesterday that when I did have the one side working last night I did have tone controls for that one channel, due perhaps to the green line that runs from eyelet 7 to again the output jacks ?

These are all just ideas I have from looking at the unit itself. Again, I won't be able to test it out until tonight. I thought I dida good job soldering, but I will be the first to admit it was one of my "rookie" mistakes. I remember wiring in the top with both wires and then I was struck when I found I had to wire a third from the bottom. Probably pushed out or loosened the top 2. But a good lesson, and we'll learned as I went through and redid all my other connections.

Now to ponder why only one channel was working on the only output I had, the phono. If I can find something about that reading or looking at my unit I will be one step closer.

I am going to Google oscillation and find out more about that.
 
It's a good bet this was an issue of a loose wire somewhere. You may have fixed it by reworking those connections, we'll see how it goes when you get a chance to test.

A tube going into saturation as gadget73 says would do this, and that problem could be caused by a shorted or too-small cathode resistor.

My personal theory for why one channel temporarily works is signal is feeding through the power supply from one to the other. This always happens to a limited extent, which is why some amps may use separate power supplies for each channel. For whatever reason, the left channel or the power supply itself might become more sensitive to this when it's only partially charged up.
 
jharris said:
A tube going into saturation as gadget73 says would do this, and that problem could be caused by a shorted or too-small cathode resistor.
Click to expand...

Hmm, ok. I put new boards with new caps and resistors. So do you think it could be one of these new ones?

Yesterday when rewiring this I notice a lot of old caps and resistors from the vol pots to on the rca jacks and elsewhere. Could it be one of these? If the wire job I did today doesn't fix it of course.

Please excuse me if my response seems silly if they would not affect the tubes, as I admit I know little on these and am learning. But I do enjoy tinkering around with old gear. Hopefully I can gain a little knowledge as I have many pieces of vintage gear I would love to go through. Thanks
 
if the old caps in place were passing signal with the original boards, I'm inclined to say that probably isn't the issue. They may not be 100% but they likely aren't causing the channel to be dead.
 
petercapo said:
+1 for this possibility. The phono board was changed-out, which would have required manipulating wires to the selector switch.
Click to expand...

You are correct, when I took out PCB 6 phono board, I decided to snip the wires instead of desoldering as not to burn the original board, and rendering it useless.

In doing so, I was left with the very short (sometimes too short) wires to try and get back into the proper eyelets (what is the proper name for these holes?) I would straighten them out manipulate them to barely reach the hole. I had no extra wire, today I brought some and as I am resoldering the PCB 6 now, I am replacing the too short of ones. Along with redoing the others.

Again, chalk this up to my rookie ways, but even reaching to resolder a wire I am knocking off ones that were barely soldered in place. I did the best with what I had to work with.

Please rest assured that the boards will be properly soldered in a very substantial way. I have learned to make the wire long, put it in the socket after attached to the coresponding tab soldering it and then removing excess from behind the board. Just in case there is still something awry with the unit after these step. Soldering should not be the issue, valuable lesson learned.

Thanks, Joe
 
I am not going to pretend that I have done a fantastic job and these things going wrong with my project are somehow "not my fault"

I realize that I am a beginner and have much to learn and will not act as if I am better than I am. I know that through practice and patience I will grow and learn.

With that being said, I do honestly appreciate all responses and all advice.
 
petercapo said:
No need to be apologetic. But, unfortunately, if you did significantly stress the contacts on the selector switch, even replacing the wires with longer ones may not solve the problem. The switch contacts, well, lose good contact when stressed. Might not be able to reestablish dependable contact but it's worth trying.
Click to expand...

There is hope, I was able to salvage mine for the short term . I have a new one waiting for installation.
 
Did you start with the basics and make sure the signal is even getting to the board. A simple continuity test or measure from RCA input jack to eyelet connection on the board would make sure of that. Or compare resistance between the working channel and bad channel.
 
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