Trying to recycle a Peavey into a T'Wreck...

[titanicslim]

My lead man gave me his old Peavey Classic 30 and I discovered something interesting on its schematic: the B+ is the same as that called out for the TW Liverpool (Well, within one volt, anyway) I seem to recall Bob-I and maybe one or two others doing Dumble clones from them but has anybody done a 'Wreck?

I'm not all that excited about the way Peavey power the filaments (nor do I understand it ) so I'm installing a little Hammond unit that supplies 6 amps of 6.3v in a nice airy chassis (reclaimed from a TKO bass amp ) I'm also not gonna bother with the PV OT, since I've got an unassigned H-1645 and I'm just very fond of those. Maybe I'll try the Peavey unit on something else when I'm desperate and needy.

Does anybody have any experience with this type of operation and know of something smelly that I'm about to put my boot in? Please tell me if you do. If this thing takes off it may get a better PT later on but with me it's not a bad idea to try a cheap one at first as I crowd these projects into a hectic schedule and... well, you know

[sliberty]

Hey Slim. Good luck on the build. It should be really fun. I built my Express into an old Univox PA head (I call it the UniWreck). I didn't really keep anything that was there before. I stripped it down to the bare chassis, and then scraped and painted the chassis (which was rather rusty). Everything else is new in mine.

[Bob-I]

I have several Peavey conversions. I like the old hybrid PV's for Dumble clones, the iron seems to work out fine. I also have a Classic 30 and I agree about the heaters, I added a filament xformer too, then built an 18 watt Marshall into it. I too scrapped the OT.

[titanicslim]

Thanks for the encouragement, guys!

A Marshall 18, huh? Hey, now- That bears thinking about....

Dave

[titanicslim]

Steve- Is this your website? http://www.freedomtubeamps.com
You made this Mini Wreck? As Billy Budd said, "I am impressed!" Well done Now that's what a single-ended amp should sound like
Dave

[sliberty]

Dave - yea thats me. Thanks for the kind words. Feel free to spread the word about my MiniWreck

[juse]

Dave - yea thats me. Thanks for the kind words. Feel free to spread the word about my MiniWreck

I listened to your soundclip - very nice. Reminds me of old UFO. Definitely has that classic sound.

[sliberty]

Somehow this thread has shifted to my amp, not that I am complaining mind you.

I am very pleased with the way the MiniWreck turned out. The clip was done with the EL84 installed, but it also takes a 6L6 or a 6V6, and my next build will also be able to handle the current required for an EL34.

I am also really happy with my Llama Roja pedals. As soon as I can get a decent clip recorded, I'llput it on my site.

[titanicslim]

Back to the Peavey (though Steve's amp is much more pleasant territory )
Those yellow secondaries (the schemo says "orange") besides providing ac to the heaters- they also send -15v to some unknown point and are used in the PV circuit for bias.

Do I need 'em for the Liverpool?

Aw, Geez, don't pay any attention to me. I've got a huge ear infection and my head is swollen to twice it's normal size- in other words three times normal size. I'm going to bed.

Dave

[titanicslim]

OK, now I've got a problem I didn't foresee.

Everything's together- almost, anyway- but no juice to the circuit The PT is putting out a little more AC than the advertised amount, just like it should, but everything after the rect. diodes, nada. In the power supply, nothing. Well, a little neg vdc or nothing. The heaters got plenty of voltage. (They have their own trannie.)

Then I just realized that all the primaries it has got are a blue and a black, which I hooked up to the pwr switch, and all the HV 2ndaries it's got are the two reds which go to the diodes.

Am I missing something here? Why is there no "-0-" in between those two 275s, or whatever they are? If there is no center tap on that HV winding, ...wthatb

The diodes are good. It is a ground (earth) thing, right ? Bob

Dave

[mlp-mx6]

What kind of rectifier circuit did the original have? Full-wave, or bridge rectifier? The bridge is used if there is no center-tap, FW used if there is.

[titanicslim]

mlp

Here is the schemo:
http://www.schematicheaven.com/newamps/ ... ssic30.pdf
It's in the lower left corner, right above the one for the bias and the heaters.

D

[mlp-mx6]

Yep, that's a bridge rectifier. Notice how the 4 diodes are aligned? The ground is generated at one corner of the bridge, and the output is the opposite corner. The 2 HV taps go on the other 2 corners. If you have a full-wave rectifier (as if you had a center tap) that will not work. You'll have to rewire your rectifier to be a bridge.

[titanicslim]

Yep, that's a bridge rectifier. Notice how the 4 diodes are aligned? The ground is generated at one corner of the bridge, and the output is the opposite corner. The 2 HV taps go on the other 2 corners. If you have a full-wave rectifier (as if you had a center tap) that will not work. You'll have to rewire your rectifier to be a bridge.

Is this because of the way the xformer is made? Regardless or the type of schematic I'm trying to replicate?

OK, let me add one more dumb question to the previous one: should I also go ahead and add the slo-blo fuse and the el cap, as shown, before that rect.?

This is a perfectly new concept to me. And I'm dumb.

D

[mlp-mx6]

Is this because of the way the xformer is made? Regardless or the type of schematic I'm trying to replicate?

It is solely due to the xfmr not having a center tap. To get the voltage out of this xfmr you must use a bridge. Period.

OK, let me add one more dumb question to the previous one: should I also go ahead and add the slo-blo fuse and the el cap, as shown, before that rect.?

I would think that the fuse is a good idea. Not sure about the ceramic cap. (not electrolytic)