What to build? (salvage iron)

[eniam rognab]

hi all!

picked up a Scott Stereomaster type 222 for iron. parts have been salvaged, new power transformer (note the cutout), converted to SS rectification (maybe, looks like there is a bridge in the schematic...), ugh....

too much for me to repair and i bought it for the iron anyway. amp is designed to run a quad of 7189s with two output transformers. can i use EL84s?

any idears from you experienceders? im not opposed to a stereo like "hi-fi" sounding amp, it would be nice to have a tube PA with all kinds of inputs; any schemo recomendation i can reference? simple, some tone controls and a volume pot is all i would need, prolly dual gang and i'll just tear one out of it... use a different chassis too... i also grabbed a schemo of the unit itself so we all know what we are working with

thanks in advance for any suggestions, i know this isnt a guitar amp per-se, but i am open to any and all suggestions, i may have some time tomorrow to rip out the iron and test the voltages. also, let me know if any of you would like some of the salvaged caps or anything, just throwing that out there cuz i wont use them.

have a great wednesday!!

[Leo_Gnardo]

There's been a rash of hi fi tube amps converted to guitar over the last 20 years, often on the original chassis. Haven't done any myself but you can scrounge up some photos.

Should be able to use EL84 instead of 7189. Since you are planning to go to a different chassis why not use 6V6? If I'm not mistook the OT primary Z should be compatible.

PA? With @ 15 watts/ch available, that's not much power for a PA. Other than guitar amp, you have the basis of a darn nice small stereo amp if you build nice & simple on a new chassis as you plan to.

[Phil_S]

Nice for salvage! I love this type of project. Plate voltage looks to high for regular EL84's. The schematic says 410V, and that's with a 5AR4. (I'd guess over 450V with ss recto.) I'm doubtful it is actually that low, particularly in light of today's higher wall voltage. You might look at Sovtek EL84M.

You might be a whole lot better off with 6V6's or maybe consider 6L6's. I'd assume an 8K primary on the OT. I'd probably test for turns ratio on the OT's to confirm what I'm working with. It's a little bit of effort for useful information.

If this were mine, I'd pull those old caps carefully and test them for leakage. If they test good, you can use them! There is a thread here somewhere, someone explained to me how that's done.

[Kagliostro]

Consider also 6P14P-EV or 6P14P-ER, a rugerizzed version of EL84 tubes

http://www.tubes.ru/techinfo/HiFiAudio/6p14pev.html

K

[eniam rognab]

ooooh, im liking these suggestions for big bottles! only built small bottle output tubes so far...

i misspoke when i said PA, i did mean like a small stereo amp for music listening to, not creation (distortion). hit the nail leo again, you read through my jibbah jabbah and got my drift.

oh and kagliostro, i have some 6P14Ps from Bob S. and they are great!! gonna pick up some more when my ship comes in.

yeah, thanks for the replys guys! i have some time today to research some 6V6 powered stereos, gonna go for simple here, not all this fancy Scott crap im not about to sort through! i can pull the transformers today too, hopefully, see what im workin with

thanks all!

[Leo_Gnardo]

i did mean like a small stereo amp for music listening to

I'd suggest start out with something familiar: just copy the output section of a Deluxe Reverb. Maybe one extra triode stage if you really need the gain, and you might, those Fender outputs take about 5VAC to drive 'em to clip.

[Phil_S]

The PT looks big, but suspect it can only handle the current for either 4x 6189 or 2x 6L6. I was thinking you can build a nice guitar amp and set aside one OT for later use. It looks like there will be more than adequate filament supply and this may explain the size of the PT. If you want to build a stereo, you'll need 2 pair in PP and I'd look at 6V6 for that on account of the expected B+. In fact, I think I'd specifically look at JJ tubes in light of the voltage. I'm not sure what those Ruskie tubes are good for in the way of voltage, so you be the judge of that.

If you are willing to put more money in the pot, consider a choke input design to reduce B+. For this, the choke has to be rated for the full mA draw of the whole circuit. That will give you safe voltages for EL84, and possibly low enough for 6AQ5! A tube rectifier with choke input will probably get you down to 300V or so.

+1 on what Leo says.

Nice project material there. I'll say it again. I like it!

[eniam rognab]

thanks for all the input guys!

i am still in decision mode, this could last months, hahhaha. guitar amp with spare OT or tube stereo?... hmmm i will research my options today, thanks for the leads guys!

i also got a scott LT-110 fm tuner, also non-operable. i got it for the PT which cant handle much current, theres no power section on this thing, and i have a radio buddy that wants all the other stuff... So i plan on doing a High Voltage benchtop regulated power supply, with like a VVR in there or something fun to kill myself with

oh yeah, a BUNCH of other stuff, this is just the coolest. i got a haul of JAN 6SL7s plus lots of other cool stuff. gonna be a loud summer!!

[eniam rognab]

i like the choke input idea phil! i dont use standby anyway and i have these big (i think) chokes that are ~14H, this one i pulled out says it tested at 16H but by who/where/how i have no idea...

do you think this can handle the current?

[ampfab]

I think I would use a 5u4 rectifier, el84 power tubes, and build an AC30/DC30 type amp. sell those two output transformers on ebay and buy a nice suitable AC30 type output transformer.
it always turns out nicer when you pull the transformers, sockets, coupling caps, and build into a guitar type chasssis.

[eniam rognab]

I think I would use a 5u4 rectifier, el84 power tubes, and build an AC30

just did that on my half power rocket! hahaha, i wanna do something else!!

haha thanks for the suggestions though, i always appreciate any input i can amplify.

sell the OTs? bu bu but thats why i bought it!? are they more valuable than i thought? like are there "Scott" people out there that want these?

[Firestorm]

How about a stereo guitar amp with a quad of 7591As? PT should be able to deliver enough current and 7591s can take the voltage.

[ampfab]

sell the two, small, scott transformers as a pair. plenty of hifi guys who'd want them. then, buy exactly what you want. took me a long time to figure that out for myself.

[eniam rognab]

sell the two, small, scott transformers as a pair. plenty of hifi guys who'd want them. then, buy exactly what you want. took me a long time to figure that out for myself.

thanks for the tip buddy i just may do this, since i paid almost nothing for them, would have paid what i did just for the tubes i got in the deal

funny thing is, i have WAY more OTs than i do PTs... you may be onto something i probably have a comparable OT... maybe turn these two into an PT!

thanks again all! cant do any ripping apart and measuring today though, i just got a digital scanner and i am backing up ALL of my personal injury documents, put them in the cloud FOREVER, my house could burn down and id still get every f-ing penny from that (*&(%^%&$^*er, but god, the installation and finding the drivers was a nightmare!

i want a tube powered scanner! the tone sucks on this thing.

[eniam rognab]

How about a stereo guitar amp with a quad of 7591As? PT should be able to deliver enough current and 7591s can take the voltage.

oh you devil!! that sounds killer!

i used to be indecisive but now im just not sure....