PAS 3

[Slartibartfast]

Hello all,


I have a PAS 3 that I have upgraded. The problem I am having is that one channel is not as strong as the other. I have replaced both boards with exact copies from Vintage Electronics. I have removed the tone controls (They were in bad shape. Pots did not turn freely and there was little difference in the sound.), The selenium stack and original filter caps have been replaced with an upgrade board.

Could it be the volume control pot is a little flakey? It does need replacing as it introduces a little static when turned up or down.


Thank you,

Robert

[kheper]

You could take voltage measurements from
the outputs of the flaky and not flaky pots to
determine if it is the pot or a component
before the pot.

[erichayes]

Hi Robert,

First thing is to determine if the balance control knob is installed correctly. Dynaco was fond of putting knobs on cockeyed to compensate for circuit shortcomings. My own PAS-3's balance control is at 9 o'clock for full left, which puts left-right balance at 12 o'clock and full right at somewhere around 6:30. If your knob isn't set like that, try resetting it and see what happens. If it is set like that already, or if resetting it exacerbates the problem, get back to us for step 2.

[mesherm]

I have two PAS-3x and while I was inside I treated all the control pots with Caig Labs Deoxit (red). I have used this stuff for years on contacts and pots and it works great. I have a bottle with a pinpoint metal tip that works great for getting into small openings. Follow that with a quick blast from a can of dust-off and it gets to all parts of the wiper.
All the pots on both PASs are silent now. The stuff isn't cheap but I wouldn't be without it. Its good for cleaning the original RCA jacks on the back of the PAS and on all the switch contacts and shafts.

http://store.caig.com/s.nl;jsessionid=a ... tegory=188

[Slartibartfast]

Hi Robert,

First thing is to determine if the balance control knob is installed correctly. Dynaco was fond of putting knobs on cockeyed to compensate for circuit shortcomings. My own PAS-3's balance control is at 9 o'clock for full left, which puts left-right balance at 12 o'clock and full right at somewhere around 6:30. If your knob isn't set like that, try resetting it and see what happens. If it is set like that already, or if resetting it exacerbates the problem, get back to us for step 2.

Full left on mine is at 8 o'clock and full right is at 4 o'clock. That seems right. I measured the top and middle lugs on each of the volume pots and at a given volume setting, one reads 151k ohms and the other reads 115k ohms. This does not seem right. What say you all?

[TomMcNally]

Have you tried Eric's method of re-centering the knob ?
I'd try balancing the sound, then putting the knobs on
so that they are in the positions you want them to be,
and see how it acts.

[Slartibartfast]

Hello all,


I am back and my PAS 3 is still up to its old tricks. I played with the balance and that did not help. What I discovered is that the bass is what is lacking in one channel, when I listen to the CD player that is plugged into the SPARE input. When listening to vinyl, going through the magnetic phono input, the output is equal.


I have replaced both boards with modern copies of the original circuit and new tubes. The tone controls have been removed from the circuit. There are still some capacitors that are original. One of them is wired between to terminals on the selector switch. I was thinking these tired old caps maybe the case of the problem. What do you all think?

[EWBrown]

Those original ceramic (and other) caps and PECs (search for "Those Pesky PECs" could be the culprit, seeing that the unbalence doesn't affect all the inputs equally.

ANother possibility, the selector switch may have some dirty / corroded contacts. Back when these units were built, they had no idea that these would still be in use 40-50 years later :o

just an early foggy monday morning SWAG Yellow_Light_Colorz_PDT_09

/ed B in NH