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I have a pa100 here that someone has done some wire clipping on. Didn't have any sound, tubes lit up though. I found a wire cut and put it back. Now I have sound. It does not sound as loud as it should be and the power tubes don't change when standby switch is flipped. Also there is two wires coming thru chassis from filter caps, the green is connected to the chassis ground, the white wire is not connected it has been cut. Any ideas where the white wire may go?
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There are probably several stages of filter caps, so it depends which ones. The main ones go to the standby switch. I'm not sure what you meant about "the power tubes don't change when standby switch is flipped". One way you should get sound, one way you should not.Originally posted by Enzo
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Compare your wiring to the schematic. I had one of these and I was surprised to find a hot B+ wire - one that shouldn't have been there, according to the schematic - leading from the doghouse into the main chassis that had been cut without being insulated or anything like that.
I'm pretty sure they just used the same filter cap board as they did for Twin Reverbs, and that extra lead would go to the tremolo oscillator - which the PA100 doesn't have. Instead of taking the five seconds to unsolder it, or at least clip it off right at the solder joint, whoever assembled the PA100 just cut it off somewhere in the middle and left a live 400-ish volt wire dangling inside the grommet. The one I had survived fine for 40 years, but it definitely made me look closely at everything else inside that beast.Comment
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No real way to know from this description and it would be very dangerous to guess without knowing what it connects to.Originally posted by pnut5150 View Post
Please follow the wire back under the cap can and find out what it connects to, then you can figure out exactly where it should go by referring to the schematic that G-one has posted.
If you can't figure it out tell us what it connects to and we will guide you.Comment
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YES the white wire is cut and left dangling. You can remove it completely, this is the safest thing to do. It was cut at factory, apparently, just as noted above for trem oscillator. It was never connected to anything in the PA100 - they are all like this.Comment
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Gotcha on wire was cut from factory. What I mean by the tubes not changing...when you turn it on the tubes light up, when you flip the standby switch (to where you have sound) I do have sound, nice and clean. However, there is no "blue" glow in the tubes, they don't get any brighter, meaning they stay the same they don't look like no more than just the heaters working...it is loud, however it does NOT seem as loud as I think that it should. Voltages on power tubes seem correct, but I will look over schematic also.Comment
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Do you have good screen voltage (pin4) at all the power tubes? The schematic shows it to be in the 435V range. I try to always check the resistance of those 470 ohm resistors at the power tube sockets anyway.Originally posted by Enzo
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What kind of replacement pots do you recommend? They are all 250k's..Any idea what size shaft? Any other specific info on the pots? Are they Logs?Comment
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