Fender Pro Reverb- not enough clean headroom!

[billyz]

For starters, the 180k plate load is going to distort the signal very soon. Also, Did you check/replace the PI tube? A weak one will cause major distortion.

[caveing]

For starters, the 180k plate load is going to distort the signal very soon. Also, Did you check/replace the PI tube? A weak one will cause major distortion.

that entire mod really didnt change the gain that much- more affected the eq. but that's the normal channel- the vibrato is completely stock and the cathode caps are seperated now.

tubes? yeh i tried that before making these posts

[martin manning]

Looking at the gut shots I'd say that you could tidy up the leads a bit. Look closely at the Fender layout drawing and try to make your leads from the board to the tube sockets look more like that. The leads going to the power tube grids seem out of place... I think I'd reroute those and in general make crossings at right angles as much as possible to minimize unwanted coupling and run all the leads down against the chassis. Do try branching the power supply and see if that helps. This thing is very close to a twin reverb- nothing fundamentally wrong with the layout.

[caveing]

Looking at the gut shots I'd say that you could tidy up the leads a bit. Look closely at the Fender layout drawing and try to make your leads from the board to the tube sockets look more like that. The leads going to the power tube grids seem out of place... I think I'd reroute those and in general make crossings at right angles as much as possible to minimize unwanted coupling and run all the leads down against the chassis. Do try branching the power supply and see if that helps. This thing is very close to a twin reverb- nothing fundamentally wrong with the layout.

i'll start working on that as soon as I can, hopefully tonight will allow me to try the thing above.

I just found out something that I guess is generally not recommended in amps. I've been using solder with silver content in this amp. Can anyone tell me more about what's wrong with this, or just if it's that bad? I just read that you shouldnt use silver solder in tube guitar amps.

Thanks

[caveing]

Caveing, if you want to give this a shot here's an easy mod to test the theory of what Colossal is saying. This splits the power supply for the reverb recover and mixing stage from the preamp gain stages without getting into the doghouse. The electrolytic I show as 22uF, it could be 16, or even 10.

So I just tried this as suggested- and unfortunately the sound remained the same. I did use a 10k resistor though. As that was the closest 1 watter I had. It may have helped a little bit- but it didnt change anything drastically.

Another thing of note that I believe I forgot to mention is that the amp is MUCH less bright now. It's not super muted or like it has a blanket over it. But I usually run treble at 8-10 and bass at 1-3... sometimes I do bass higher though- but if I put the bass up higher than treble- say bass at 10 and treble at 8- it does get pretty muffled sounding compared to how it used to sound. I used to get super cutting highs- especially with my weber california, tantulum cathode bypass caps, metal film resistors (those things really did make the amp a good deal brighter IMO, especially the tant cathode bypass caps) The amp sounds fine at treble 10 bass 1, but not nearly what you would expect from a fender.

I suppose the amp did lose a little headroom when I installed the mids knob on the back panel around the same time I removed the death cap, extra outlet and ground switch... but there wasnt just a day tht I was like oh shit that sounds completely different. But I do remember it sounding great when I fixed my crackling plate resistors not long at all ago. maybe 3 days before I started this topic. But even then the headroom was not what it was 4 months ago, and even that wasnt really like it was a year ago.

I definitely feel like this is a progressive problem... Here's some other things that might have contributed-

partially melting some of the plastic on the wires into solder joints- i've never done this really obviously like theres a ton of insulation in that solder mix- but there could be some.

silver solder?


by the way this didnt happen right when I replaced the components in the amp to the metal film resistors and new tone caps, filter caps and all that. The amp did work perfectly fine there for a while.

Would a sound clip be helpful to anyone?

[martin manning]

Ok you've proven that the distortion you are hearing is not an oscillation on the power supply. I'd put it back to the original wiring and fix up the lead dress. That might help with the distortion and with the brightness.

Mixing lead-free and tin-lead solder is generally frowned upon, with possible consequences being brittle or unstable joints. Lead-free is harder to work with since it requires a higher temperature, and when you mix the solders you are also mixing the fluxes, and the mixture may not work as well. Inspect the joints carefully and reflow any that look suspect. Contamination with melted insulation should also be avoided, but if the jount looks good (surfaces well wettted and shiny when cool), it probably is good.

Yes I think a sound clip would be useful.

[caveing]

Ok you've proven that the distortion you are hearing is not an oscillation on the power supply. I'd put it back to the original wiring and fix up the lead dress. That might help with the distortion and with the brightness.

Mixing lead-free and tin-lead solder is generally frowned upon, with possible consequences being brittle or unstable joints. Lead-free is harder to work with since it requires a higher temperature, and when you mix the solders you are also mixing the fluxes, and the mixture may not work as well. Inspect the joints carefully and reflow any that look suspect. Contamination with melted insulation should also be avoided, but if the jount looks good (surfaces well wettted and shiny when cool), it probably is good.

Yes I think a sound clip would be useful.

will do- i think they're fine. i sucked out the old joints before replacing but yeh i guess they're mixed a little bit. all the new joints are shiny and nice looking. stabile... i feel i'm pretty good at soldering.

i just have this feeling that a transformer is dying. are the symptoms of my amp not similar to that at all?

[martin manning]

Sounds like you have the solder situation under control.

Have you changed the negative feedback resistors from the stock 820 and 100-ohm values?

A sound clip might help at this point so folks can hear the problem you are describing. On the transformer, a lot of people would sub in a known good transformer to test that theory, but there are some simple tests that you can do. See https://tubeamparchive.com/viewtopic.ph ... highlight=

[Firestorm]

I just found out something that I guess is generally not recommended in amps. I've been using solder with silver content in this amp. Can anyone tell me more about what's wrong with this, or just if it's that bad?

What kind of silver solder did you use? The higher the percentage of silver, the higher the meting point. Real "silver solder" (over 50% silver) is used in jewelry making and doesn't melt until over 1000 degrees C. If you were using that, you would have set fire to something
There are lower-silver compositions that melt around 260 degrees C. But typical electronics solder (with lead) melts around 180-190 C. We use that to minimize the chance of overheating a component.

[caveing]

FIXED! Now I'm back to the original things I dont like abotu the amp! Should I upgrade transformers to super reverb sized? Should I just do output? Or should I do both output and power so I can use a GZ34 rectifier without overly high voltages?

Thanks for the help everyone!

It turned out to be one of several things I touched up after giving my eyes a few days rest. I twisted some wires I dont think were originally twisted in my amp- untwisting them might have been it. Had a few ugly looking solder joints that I remelted and sucked up and tried to remove the grime out of.

My solder is actually 1% silver. is that okay for amps?

Thanks again!