Champ blowing fuse

[MWJB]

What size is the cathode resistor at 6V6 pin 8?

Don't forget that the cathode voltage needs to be deducted from the plate voltage, so the tube might only be "seeing" ~410vdc. Reverse polarity zener diodes are an option, but as long as your 6V6 isn't redplating, you might not have a 'problem'

[mort]

What size is the cathode resistor at 6V6 pin 8?

Don't forget that the cathode voltage needs to be deducted from the plate voltage, so the tube might only be "seeing" ~410vdc. Reverse polarity zener diodes are an option, but as long as your 6V6 isn't redplating, you might not have a 'problem'

It's a .470k but reads .611k. That's the 1w resistor that sits along side the 25/25 cap, right?

[MWJB]

Yes, that's the one. I wouln't use a resistor that had drifted that far, if you replace it with a 470ohm resistor that actually measures 470ohms (use a 5W rating) then your voltage will drop a little...or replace it with 600-680ohms to retain the current tone, the voltage will stay the same or rise very slightly, but you don't have a problem.

Be sure that you have a NOS 5Y3 installed, not the Russian "5Y3" (it's a great tube, just not very suitable for old, cathode biased Fenders).

Replace the 25/25 cap with a 25/100v and keep it away from the cathode resistor (elevate the resistor off the board).

[mort]

thanks for the tips.

Does that address the underpower situation at all? I found a couple caps way out so I replaced them and the tone improved but the volume is still very low. I replaced the 25/25 next to said resistor, and the 2/25. edit: it was the other 25/25 at the opposite end of tag board that I changed, other one is in spec.

I did notice a mistake I made, perhaps it may not matter much but you tell me... The resistor I replaced that calls for a 2700 ohm, by mistake I put in a 2200. Could that affect the overall volume level in such a way?

[riz]

Maybe it's time for a new 6v6?

[mort]

I've swapped out all tubes for known good ones and nothing changes at all.

When I get chance to I'll do a full list of voltages and post them here...

[Jag]

Please don't get me wrong in asking this question but, what are you comparing the amp to when you say it's undepowered?

[mort]

Please don't get me wrong in asking this question but, what are you comparing the amp to when you say it's undepowered?

I had considered that I may be misjudging what to expect from it because I've played fewer champs than I have other Fender models, but this thing is real quiet. It's sounding good at this point but the volume is so low that I could speak with someone from across the room in a low voice and they would have no trouble hearing me. I would say that it is considerably more quiet than average TV listening volume.

Smallest and quietest amp I've owned was a 50's Gibson BR-9. This Champ sounds about half of that, but does overdrive where the BR-9 barely would.

[52 Bill]

Have you checked the speaker wiring or tried a different speaker?

[mort]

Have you checked the speaker wiring or tried a different speaker?

I did not reverse the polarity but I did try the speaker with another amp and while not as "full" sounding as a 10" speaker or larger, it sounded fine to me.

I'll try swapping polarity, that's a good idea. I have indeed had weird results with speaker miswiring.

[52 Bill]

I was thinking more like shorted secondary wiring or speaker. That would cause your loss of power.

Some of those Champ speakers had a built in jumper on the terminals that grounded the metal basket. If the wires were reversed, it would act like a dead short on the output.

[mort]

Both the OT and speaker are brand new from weber. I don't suspect any problems with them but I suppose it's possible. The wiring all looked tight & right when I was going through it previously. I'll recheck though... never hurts.

btw & fwiw, polarity is not an issue, just checked.

[Jazz P Bass]

I had considered that I may be misjudging what to expect from it because I've played fewer champs than I have other Fender models, but this thing is real quiet. It's sounding good at this point but the volume is so low that I could speak with someone from across the room in a low voice and they would have no trouble hearing me. I would say that it is considerably more quiet than average TV listening volume.

Smallest and quietest amp I've owned was a 50's Gibson BR-9. This Champ sounds about half of that, but does overdrive where the BR-9 barely would.

How about quantifying the issue.
Hookup your DVM to speaker leads.
Set the meter to read Vac.
Turn everything up.
The guitar & the amp.
Play some chord hard & read the Vac at the speaker.
Now do the math.
Voltage squared divided by the speaker voice coil resistance.
That is the output power of the amp.

[mort]

How about quantifying the issue.
Hookup your DVM to speaker leads.
Set the meter to read Vac.
Turn everything up.
The guitar & the amp.
Play some chord hard & read the Vac at the speaker.
Now do the math.
Voltage squared divided by the speaker voice coil resistance.
That is the output power of the amp.

Ok, just did that voltage check.

most I saw on my Fieldpiece SC53 while picking chords hard was .456vac.

Speaker measures 3.7

that equates out to .769 watts?

I did the check 3 times just to make sure I was getting the same results.


Thanks for entertaining my questions everyone, I do appreciate it

[Jazz P Bass]

O/K.
Now do the same thing on the output tube cathode resistor.
Cathode side of resistor, Vac.