5E3 deluxe build with SS rectifier and Ampeg trannies!

[mikhett]

I have a power trans and other out of a junked 60s REVERBROCKET.Im an electronic tech by trade so I know my way around circuits.The power trans used a SS rectifier so a tube is out.Im trying to do this on the cheap.I will order the parts from Hoffman for his deluxe parts list.The chassis I got from ZACK HUNTER IN LITTLE ROCK FOR 50.00!

[Dave H]

What are you asking?

[mikhett]

Just wanted to know if anyone sees anything wrong with this prospective build?

[Leo_Gnardo]

Just wanted to know if anyone sees anything wrong with this prospective build?

Only advice I have: make sure your old Ampeg transformers are actually working correctly before committing to using them for your build. I've run across many old Ampeg tran's that have failed, some due to exposure to damp conditions that has caused the very thin hi voltage wires to corrode. Also OT's that have shorted secondary windings, PT's that have open or shorted windings due to abuse or just plain old bad luck. I suppose worst that could happen is you build, then find you have transformer problems, then substitute fresh known working iron. Due diligence first, check your iron any way you can, before you bolt it in & get disappointed. I do hope it works out well for you. Nothing like saving substantial $$$ by repurposing old transfomers. Best of luck!

[Chuck H]

I think most of the Reverberocket amps with the SS rectifier used 7591's. If your chassis is from such an amp then you CAN use a tube rectifier. The 7591 has a .8A filament draw compared to the 6V6 .45A. .8 - .45 = .35A per tube of surplus filament current. X2 is .7A. Now consider that the 5E3 uses two preamp tubes. Your chassis will have more. You get an additional .3A of available filament current for each preamp tube you don't use. Even if thats only one preamp tube you have an amp of surplus filament current for a 5E3 build. And as it happens a 6CA4 requires one amp of filament current. You won't even need to buy a socket since you can repurpose the preamp tube socket you're not using.

[Dave H]

I think most of the Reverberocket amps with the SS rectifier used 7591's. If your chassis is from such an amp then you CAN use a tube rectifier.

If it's a bridge rectifier then it needs four diodes. I suppose two of them could be the 6CA4.

[mozz]

It's nice to have a separate winding for the rectifier tube, even a 6ca4. I would just use diodes in the power supply and maybe a 500 ohm or more resistor of correct wattage to induce some "tweed" sag.

Pick your output tube, then measure your filament voltage, it's it's real high then you can do something about it like adding a 6ca4.

[Justin Thomas]

I think most of the Reverberocket amps with the SS rectifier used 7591's. If your chassis is from such an amp then you CAN use a tube rectifier. The 7591 has a .8A filament draw compared to the 6V6 .45A. .8 - .45 = .35A per tube of surplus filament current. X2 is .7A. Now consider that the 5E3 uses two preamp tubes. Your chassis will have more. You get an additional .3A of available filament current for each preamp tube you don't use. Even if thats only one preamp tube you have an amp of surplus filament current for a 5E3 build. And as it happens a 6CA4 requires one amp of filament current. You won't even need to buy a socket since you can repurpose the preamp tube socket you're not using.

Agree on the power tubes, but would REALLY like to know what precise preamp tubes were used in his chassis. It might have a compactron or two, or a 7199; honestly he could probably fudge it, but I tend to think precision can lead to better options, especially since the variable IS actually quantifiable...

Come now, what preamp tubes came in your chassis?

Justin

[mikepukmel]

Only advice I have: make sure your old Ampeg transformers are actually working correctly before committing to using them for your build. I've run across many old Ampeg tran's that have failed, some due to exposure to damp conditions that has caused the very thin hi voltage wires to corrode. Also OT's that have shorted secondary windings, PT's that have open or shorted windings due to abuse or just plain old bad luck. I suppose worst that could happen is you build, then find you have transformer problems, then substitute fresh known working iron. Due diligence first, check your iron any way you can, before you bolt it in & get disappointed. I do hope it works out well for you. Nothing like saving substantial $$$ by repurposing old transfomers. Best of luck!

Is there a good site you know of, maybe, with info on how to test old Ampeg transformers for those problems (besides dead short or open, of course)? Are certain year/ model worse than others?

[Chuck H]

See here:

http://www.geofex.com/ampdbug/outtrans.htm

http://www.geofex.com/ampdbug/pwrtrans.htm