Kalart-Victor 70-15 Reel to Reel Audio Amp, Re-Opening the Case

[Platefire]

yeah, it was V2a sorry! #19 in a square box which refers to the PI board layout

[sluckey]

the .02 Ceramic cap blocking DC to the grid was leaking 39VDC.

Guess what? That cap is supposed to have dc on both sides. I bet if you check you'll find there is still about 39v on the grid side.

[Platefire]

Is that coming from the cathode V2b through that 2.7K and 470K resistor? God works in mysterious ways! The buzz is gone and the amp sounds great!

[sluckey]

perzactly. Not doubting the cap fixed your problem. Just saying...

[Platefire]

Well I hate to report this and very frustrated but----I tried the amp one more time beforeI went to bed and the noise is back. It was dead silent before to the point when I turned it on I would wonder if it was working. That tone stack is pretty amazing. With treble all the way up and bass dialed back you could make your strat sound like a tele. Or on the other hand with the treble dialed down, bass up get some warm jazz tones and with it set in the middle, just a good all around setting. It holds it's clean tone until about 1:00 oclock on the vol and gradually the grit gets mixed in with the clean the louder you go. Good harmonic tones. 


After all that, best I can figure that that old replacement cap I used failed. I looked at the schematic to determine the voltage rating for the one I put in there but couldn't find it on the schematic and there is no markings/codes on any of the ceramics.

[Platefire]

Got a order in for parts that include what extra I need to rebuild the Kalart boards. We'll see what it does then.

[strmusicman]

Mr platefire try to measure all the components from the board(resistors and caps) .my opinion is to change all the resistors with metal film and the caps with orange drops caps.

[Platefire]

Hi strmusicman
I am changing out all on both boards. I ordered the Mallory 150's capacitors. I'm using mostly resistors out of my own inventory. It will be a combination of metal film and carbon.

I had it working wonderfully until something went out. Hoping changing all board parts
will fix it. 

[Platefire]

Well I come shame-faced  and embarrassed because I still can't believe I overlooked something on the amp that should have been obvious. I'm the one who had it in my possession
before my eyes all this time and it seems at some point the thought should have occurred to me 


Why after several years of thinking about this amp off and on, trying all kinds of fixes, only today I had the thought that this amp has two chassis sections and their connection between each other is loose. I located the connection screws and nuts and tightened them up with a screw driver and bingo! The noise is gone. It was a grounding connection problem between the two chassis. 

 

[Platefire]

KV

[strmusicman]

mine was with rivets ....what can i say.at least you find the solution mr platefire.

[Platefire]

Yes your right. The good thing is it's working great and I'm just enjoying playing on it, trying different guitars. Real easy to dial each one in with that tone stack