First thing I would do is check the input tubes. If that’s not it, could be voltages feeding the tubes, or you’ve got a bad component in the signal path of the input section.

G

I assume your talking about the secondary you’re taking readings on. Something is screwy there if you are. Should be a lot lower.

Also sometimes when an output trans has taken a beating you can smell it and it has a burnt smell. Sounds like yours has opened it a bit.

Usually they open all the way though but anything is possible, too bad you don’t have something to jump in to make sure.

Good Luck!

Just metered the OT, I get 60 ohms on one side, and 90 ohms on the other, neither of which is what I expected.

The series measurement agrees (150 ohms.) Primary to secondary resistance measured infinite.

I couldn’t find my bassman 100 OT to do a comparision, but will have to assume that the OT in the deluxe is no good since the brown and
blue side should agree with each other.

Regarding caps: what I always do is put a dedicated meter across the B+ cap so I can see the voltage level inside the amp. Once it drops down to about 30V i put a 22k 5W resistor across the meter terminals to bleed the capacitors out.

Then I remove the resistor to see what the voltage level is when the capacitors down stream are filling
everything back up to.

I’d just like to mention again that you’ve been very helpful throughout the process. Thank you so much!

-Dennis

Sounds like a plan. You can use anything for a load from 4 ohm’s up if that’s what the secondary of the fender silverface transformer is.

You just need it to check the symmetrical swing of the waveform. If you were checking power you may want exact but you will be able to crank it enough with an 8 or 16 ohm dummy load.

Yea, sends pics.

I got an old fender bassman 70 output on ebay if you know anyone interested.

Gary

Thanks for the reply.

I’ve got an aftermarket OT for a silverface bassman 100 that I think will work as a substitute (the bassman 100 output stage is 2×2 6L6, ~100W, probably a similar B+ voltage.)

I just need to find a 4 ohm load that goes with the bassman transformer. If I end up finding the OT and a load I’ll let you know how it goes.

My guess is that the person who actually owns this amp will probably sell it now that I’ve gotten sound to come out and we’ll describe exactly what we think is wrong.

There are people out there with spare OTs for Hot Rod Deluxes I imagine who would probably check it out.

To clarify on the symptoms for, the sound comes out half clean and half distorted for something that sounds like music played too loud of a cell phone
speaker or through a call waiting song.

I’ll try to take some pictures of the output wave form so you can have something visual to go with it once I get back to the office where I do my work in the after hours. Its a digital scope but it should get the job done.

-Dennis

Your thinking like a tech.. LOL You know enough to start second guessing the design of the amp. This sounds very logical. No, if you know what you’re doing you shouldn’t hurt your amp, BUT I’m almost 99% sure if you do this you will experience and oscillation that will be severe enough to where you can’t read the waveform long enough to get what you want.

Now on this model of fender transformer I could be wrong but usually when you hook up the primary of the output transformer backwards it squeals, it’s a phase thing. Also I wouldn’t do this without a variac.

Yes, the shorted wire could have put a hurting on your OT, sounds like you’ve checked the easy stuff. Do you have another transformer that is in the ball park you could jump in long enough to test your suspicion?

Gary

I subscribed to the newsletter to keep learning about amps and electronics. I hope you don’t mind if I ask for your opinion on something via email.

Anyway I’ve got a Fender Hot Rod Deluxe (2001 on the PCB,) that is giving me a poor distortion. With my scope on the speaker output, the + side of the output wave is clipping at around 3V, while the – side of the wave looks normal, going down to around -16V. The resulting sound as you can guess is pretty crappy.

Before I had gotten this amp the speaker cable it came with was intermittently shorting (!!!) to about 0.1 ohms, and other times insulating perfectly. I’ve replaced the cable and now I’ve got this distortion problem.

I’ve checked the output signals coming from the driver tube V3 (both A and B sides) and none of them show this clipping. I’ve swapped the power tubes and the 12AX7s around and the clipping still occurs on the + side of the output wave. I’m starting to suspect the output transformer has taken some kind of damage by having a shorted output but want to know how to check for this. I’ve got the preamp bypassed by plugging in my signal into the power amp in jack.

My question: is it safe to swap the Blue (CP19) and Brown (CP20) wires on the output transformer so that V4 and V5 are driving the opposite sides of the transformer than they are supposed to? I couldn’t think of a reason why it wouldn’t be safe aside from how the feedback is applied to V3B. I’m thinking that if the transformer is good then I should see the clipping occur on the – side of my output wave since I’ve now reversed which tube drives the + and – side of the output.

It’ll be another week or so before I get to poke around inside the amp, so I figured it would be a good time to think about my next move before I decide to do something goofy and wreck the whole thing. It would be great if you could point me in the right direction.

Thanks,
Dennis