Carvin vintage 16 low output

[g1]

One other thing I was going to mention was to check on the bias. The stock schem. says -17V on the grids and I think you mentioned -10V ?
I guess any leakage could be affecting that also, but double check after the cap fix.

[nosaj]

Yes one of the 4 caps on it is leaking half a volt.

jason

Well I replaced the one I sure thought was leaking and by golly the replacement is showing same dc on it. In the pic 2 of the pot legs are getting dc on them, the other 4 are not. The sozo is the replacement.
I have never taken a dual pot apart before. ( but I will be soon) I don't yet understand how I'm seeing voltage on both, I really thought they were separate pots with a common knob.
nosaj

[nosaj]

Well I replaced the one I sure thought was leaking and by golly the replacement is showing same dc on it. In the pic 2 of the pot legs are getting dc on them, the other 4 are not. The sozo is the replacement.
I have never taken a dual pot apart before. ( but I will be soon) I don't yet understand how I'm seeing voltage on both, I really thought they were separate pots with a common knob.
nosaj[ATTACH=CONFIG]43850[/ATTACH]

Well I took the pot out, depending on how the test leads are connected I can can get measurements anywhere from 0-1meg, 1meg-2meg or 0-2meg.
I think instead of messing around with someone else's mode. I'm gonna move it back to stock and see how things go from there.

Not really sure I'm a fan of master volumes I tend to like loud and nasty.

Will follow up tomorrow.

Thanks,
nosaj

[Enzo]

There is a difference between a leaky cap putting voltage on a node and a DC voltage appearing on a node a cap connects to. Remember those conductive eyelet boards on old Fenders?

I see the factory schematic, and I see a printed up description and instructions for mods, but is there a schematic of your amp AS BUILT? I can imagine about where this double pot is, but I want to see the circuit, I am suspicious you may have an unterminated part.

[nosaj]

There is a difference between a leaky cap putting voltage on a node and a DC voltage appearing on a node a cap connects to. Remember those conductive eyelet boards on old Fenders?

I see the factory schematic, and I see a printed up description and instructions for mods, but is there a schematic of your amp AS BUILT? I can imagine about where this double pot is, but I want to see the circuit, I am suspicious you may have an unterminated part.

Here it isHasse_V16_mod_schem.pdf

nosaj

[nosaj]

Here it is[ATTACH]43851[/ATTACH]

nosaj

Ok I took the pot out and have the caps one side still mounted in the circuit the others are flying.
The blue and the yellow ones on the left have dc that goes from .5 up to 3volts not in any order I can see. The 2 on the right no DC at all. It's starting to storm again TS Cindy is dumping a tone of rain on us.
I'll grab the voltages on the mounted side of the cap. In my head I should see no dc on the flying ends. I am using chassis ground.

Thanks,
nosaj

[nosaj]

Ok I took the pot out and have the caps one side still mounted in the circuit the others are flying.
The blue and the yellow ones on the left have dc that goes from .5 up to 3volts not in any order I can see. The 2 on the right no DC at all. It's starting to storm again TS Cindy is dumping a tone of rain on us.
I'll grab the voltages on the mounted side of the cap. In my head I should see no dc on the flying ends. I am using chassis ground.

Thanks,
nosaj[ATTACH=CONFIG]43872[/ATTACH]

Ok I put it back to the original volume control with c22 and c23 as .1uf right now just for testing purposes.
No DC on the Volume now.
Checking voltages on caps C18 C19 and C20 I have DC on both sides of the caps.Going by the Carvin schematic It looks like c18 and c20 need to be replaced C19 maybe seeing DC on both sides because c18 failed.
Does this look right as far as my thinking?
Can't replace anything till tomorrow evening.

Also with C22 and C23 being .1uf instead of .047 what effect would this possibly have on sound? I still plan on changing it but just curious.

Thanks all,
nosaj

Vintage_16.pdf

[Enzo]

C22 larger means more bottom end is possible. Someone else can do the math to see where it matters.

WHAT DC voltage? A quick in my head tells me the cathode of the tube will have a good 50v or more on it. So C19 would have 230v on one end and 50 on the other. So C18 would also have 50v on one end and zero DC on the other. C20 ought to have the 50v on one end and the other end maybe 6 to 10v from that 3.3k resistor.

C18 has voltage n both ends?

[nosaj]

C22 larger means more bottom end is possible. Someone else can do the math to see where it matters.

WHAT DC voltage? A quick in my head tells me the cathode of the tube will have a good 50v or more on it. So C19 would have 230v on one end and 50 on the other. So C18 would also have 50v on one end and zero DC on the other. C20 ought to have the 50v on one end and the other end maybe 6 to 10v from that 3.3k resistor.

C18 has voltage n both ends?

C18 296Vdc / 42 Vdc
C19 270 Vdc / 42 Vdc
C20 44Vdc / 4 Vdc

Guess I was confused with Voltage on C20, thought that you wouldn't have DC on Grids of any preamp.
Thanks,
nosaj

[Enzo]

Grid voltage is considered with respect to cathode voltage. You are measuring those grids to ground. The "real" voltage there is higher than that. The grid voltage will only be a volt or so more negative than the cathode. The fact that both of them are about +50 is irrelevant to the tube.

But I don't understand your C18 readings. On the schematic I see the right side of C18 connects to the grid and C19, your 42v. That leaves the left end of C18. Where would 300v come from? If the cap were leaky or shorted, then all we would see would be the 42v. I see no component failure that could put 300v there. If it really is at 300v, then it almost has to be some sort of short on the board, like wires touching, or a bead of solder, etc.

[nosaj]

Grid voltage is considered with respect to cathode voltage. You are measuring those grids to ground. The "real" voltage there is higher than that. The grid voltage will only be a volt or so more negative than the cathode. The fact that both of them are about +50 is irrelevant to the tube.

But I don't understand your C18 readings. On the schematic I see the right side of C18 connects to the grid and C19, your 42v. That leaves the left end of C18. Where would 300v come from? If the cap were leaky or shorted, then all we would see would be the 42v. I see no component failure that could put 300v there. If it really is at 300v, then it almost has to be some sort of short on the board, like wires touching, or a bead of solder, etc.

Completely took it out and looked over nobeads or wires touching when I put it back together.
Now C36 measures 229v on one side and 240v on the other. Does that sound right?
It is shown on the Carvin schematic one side connects to r8 and c18 other side connects to r8 and c41 and c12.
nosaj