Thoughts on how you'd proceed with this

[ratgon]

Hey all, first of all, I'm gonna post some pics so I hope they actually post. Resized them and everything so fingers crossed.

I picked this up off Craigslist a couple weeks ago for a hundred bucks. I bought another one for about the same price...an Ampro. Bothere very cool amps from 16mm film projectors from what seems to be the 40's or 50's. Still doing research. This one here, the victor actually works and has a pretty incredible tone. But it clearly needs work. Very noisy and i'm sure it's laden with all sorts of potential safety issues.

Just curious as to how'd you all approach doing something with this. I'm super new to learning how to even finish basic kits and have them actually produce sound let alone attacking a rebuild or refurbishing of something like this. But even in it's current state it sounds pretty amazing.

Just would love to hear what you all thought.

Let's hope these pics post.

Thanks.

[eleventeen]

Wow, I never knew Victor projectors (which were considered VERY high quality projectors) were part of Curtiss-Wright, who was of course a famous aircraft mfr.


That Victor cabinet is superb, beautiful looking. I'd be sorely tempted to copy the design and mass-market it, except manufacturing things in the US is nearly impossible. And JVC would probably sue you into oblivion. (Japan Victor Corp)


Esp if you are a newb, you're going to face some challenges working in such a small chassis. Look at all those transformers! Obviously 2-3 of them are coupling/interstage transformers. That's certainly unusual for a guitar amp but likely responsible for the nice tone. No apparent "aux" input jack for a guitar.

I don't have any brilliant suggestions as to what to do. I would probably stare at it for a few months before hacking into it and try to envision the entire process. The wiring in the Victor is all tied-up into a neat bundle and will get unruly if you take it apart. Knobs on the narrow end of the thing, because it was designed to fit into the innards of a projector......kind of opposite normal for a G_amp.


Standard "rejuvenate old tube stuff" rules would apply: replace ALL caps. One_at_a_time so you can't make mistakes (ha!)

I will let others chime in, I don't have any great ideas for you.

[sluckey]

That's a nice looking unit. Very high quality workmanship. I'd put it on a shelf and carve some notches in my belt before diving in. IOW, fix those other simple amps first. That'll give you some more experience and also give you some time to think about what you want to do with it. It would almost be a shame to butcher that nice work.

[dunner84]

I am going to have to agree with sluckey on this one. I have tackled similar projects in the past, and you need to have a understanding of what is going on in tube amps. I am a solid state guy by trade, so it took some time to get used to tubes. I am still learning the quirks.

If you havent built a kit, build one. next thing I would do is building a simple amp from scratch with maybe an upgrade or two, like switchable NFB.

Also, go to youtube and watch all of uncle dougs videos. I think he was a teacher by trade. He is very easy to follow and has videos for most things tube amp related. The other thing I really like about uncle doug's videos, is that he always works from a handdrawn schematic, so you get used to hearing a component name, where if falls in the schematic, and where it is usually located in a chassis.

Get used to the basic components in tube amp schematics. Once you have that basic knowledge, you can look at the circuit, and things will be apparent to you.

In my experience, old film equipment can be modified to be some ofthe best sounding guitar amps. They don't require much to get there either. It is worth shelving until you have some more experience though.

[eleventeen]

I would immediately trace the front of that cabinet and get a few T-shirts made, though! Exceptionally cool logo. That would get my "mess with it" mojo out of my system.


I would again suggest holding off & doing some more 'net research before tearing into it. Somebody somewhere will want that and even tho maybe you paid real $$ for it, maybe they trade you 2 or 3 amplifiers or other things for it where you end up with more, and easier-to-work-with something or other(s) and they get their nirvana projector. 

[ratgon]

Thanks all. Very much appreciated. If I've learned one thing so far it's knowing my limitations. There's no way I'd gonna into doing anything with this yet. I did however, bring it up very slowly with the variable and used a dim bulb to check once I thought it was ready. Someone at some point did convert of of the old screw on type of mic inputs into a 1/4 guitar input. So I've been able to play it enough to know it has the potential to an awesome little amp. The guy also through in what he claimed were a matched pair of original Tung Sol 5881's. Who knows about the veracity of that claim but they definitely very old and still wrapped in original plastic and box packing. Were/ are 5881s an option to the 6L6 GAs that are in there now?

Anyway thanks for input. Ultimately I  want to keep it as original as possible. Seems that building head cabinet Is clearly the way to go. I wonder if can drive regular 12" speakers or if it's designed to really maximize using the electro magnetic and its oughly 50' of speaker cable

And fear not, I won't be new guy barreling into ruining everything with just enough knowledge to kil me.

So thanks for checking it out

And oh yeah! Uncle Doug. I watched all of his videos. In fact the first silent amp issue I encountered was after firing up the Supro Tremo verb clone he just finished posting the design and building of. I've learned so much from that guy!

[ratgon]

By the way, I have found a schematic for it. It's a Victor or RCA Victor model 60B. It's very hard to read. Still looking for more info.

[eleventeen]

Some of the later RCA projectors have really exceptional amps in them. Not that this is a bad one. Often powered by 12AX7(s) >  6973's. These were simply bulletproof machines, classic American iron. Rugged, overbuilt. The bugaboo, as you see, is adapting the form factor of the raw amp into something that resembles a guitar amp that you can carry around should you so choose, instead of a desktop chassis with separate speaker cab.

[ratgon]

Exactly. It would almost be a sin not to keep the speaker in that beautiful cab. And since the lugging around will be very minimal, basically from my house to the studio with extended periods of time a
T each place.

Honestly, while I do play guitar and actual just relea record, a double album no less, my main drive to build these things is purely for the love of simply learning and creating. I'd be happy to just make amps for my friends for just the cost of parts and maybe a nominal fee for my labor. I have a bunch of friends have some very, very nice home studios. I'd love to have a couple of my builds in their gear arsenals.

[eleventeen]

" The guy also through in what he claimed were a matched pair of original Tung Sol 5881's"


That's awesome, potentially worth more than the amp!


Sure. 5881's ARE 6L6's, for the most part. More like GB's vs GA's. But the differences are quite minor.

[ratgon]

Thanks...I really have no idea if these are original or what. Evidently they have been reissued but the tube and packaging are very different. It's all just icing on the cake to me at this point but it would be cool if they were the real deal. Now, if they were, would they be recommended over the 6L6s?

[eleventeen]

Suweet!! Those look like genuine 5881s, maybe from ~~1960 judging by the date codes which I can't fully make out the way you have those rotated in your pix. Year of mfg is the 3rd and 4th digits from the right. I don't think the Chinese or Russian ones say "Made in USA"! Put those away, my friend. Somebody will pay you good money for those. A truly matched pair of those might fetch as much as $250 from a true fetishist.


I have never found there to be any real difference. 5881 are a ruggedized 6L6 that were made or at least brought out when "6L6GB" was the current revision of type "6L6". If you look at LATE Fender tweed amps and some of the early white Bassman/Bandmaster schematics (see Doug's library) they are usually what are specified. They are essentially 6L6GB with about 1 watt less power rating, mostly due to the slightly reduced glass bottle. They are 6L6 for all practical purposes.


Congrats! Those are jewels.

[ratgon]

Thank you for the info. I'l stash them away. By the way the full number code read
"322DB3"

[HotBluePlates]

I really have no idea if these are original or what. Evidently they have been reissued but the tube and packaging are very different. ... it would be cool if they were the real deal. ...

Yes, those are real-deal U.S. Tung Sol 5881's. They have all the hallmarks of the original tube. Nice!

... Now, if they were, would they be recommended over the 6L6s?

The original "5881" is a 6L6; more precisely, a 6L6WGB (6L6, "W" - military designation, "G" - glass envelope, "B" - 2nd Revision after metal 6L6 and glass 6L6GA).

The 5881 has some ratings increases, and is designed to be mechanically rugged in a high-vibration environment (like in your bomb-sight on a B-52). It is rated for higher plate dissipation (23w vs. 19w for the 6L6/6L6GA), but that won't matter in the projector amplifier. So both tube types (as well as the metal 6L6) will work. Additionally, so will probably any other 6L6 variant, assuming they will physically fit in the space afforded.

By the way, I have found a schematic for it. It's a Victor or RCA Victor model 60B. ...

Can you attach the schematic here?

The speaker looks like it might be a field-coil type with the output transformer mounted on the speaker basket. If so, the speaker is an integral part of the amplifier's power supply, so the two should be used together. The schematic might help clarify that (or highlight that there's just some kind of line-matching transformer on the speaker).
 
 
 
NOTE: Eleventeen posted first, but we agree on all essential points. Separately, if you need the old-school metal 6L6, 6L6G or 6L6GA, I may have a line on a source for those for cheap prices. I doubt they can guarantee matching, though that may not matter in this case (I doubt you need screaming clean power from a projector amp).

EDIT: Photo of a Russian 5881 attached. Aside from the screened labeling on the tube base (which could be faked), note the lack of the 3 horizontal mica supports holding the top & bottom mica spacers whithin the tube. Also, while the plate is the same shape (which is unique to a 5881), note the Russian tube has notches at the top & bottom of the plate material. Your tubes (the real Tung Sol 5881) have no such notches.

[jjasilli]

It's great that you have the schematic.  The only real alternative would have been to draw it yourself.  Reconciling the ad hoc, point-to-point  layout of vintage amps with the schematic should be quite an experience. 


You should replace all the caps and resistors in the power supply.  The best procedure is to post a copy of the schematic above your workbench.  First take detailed photos with a camera or smartphone, and draw diagrams in case you get confused later.  This can happen to anyone due to those old ad hoc layouts.  Proceed in an orderly fashion working "backwards" from the Power Transformer secondary winding.  Try to remove & replace only one component at a time.  (This may be difficult due to the cramped chassis, but don't strip the chassis bare!)  As you replace components, mark-off your progress with a highlighter pen on the schematic.  With this procedure you can keep your bearings.

[eleventeen]

Hmmm, different date code than Tung Sol 6550's then.


https://www.tubeworld.com/5881.htm on this page you can see 3rd & 4th digits from the right for 1959, 1961, 1963


I have 4 qty grungy 5881 with a similar date code as yours, I don't know how to decode it.


On this page you can see 6550s from 1965 and 1972. https://www.tubeworld.com/6550.htm


Please don't be screwing around with those as test subjects in an amp you are working on. They are pretty valuable and it would be tragic to blow them accidentally! If they work, the 6L6G or GA you show in your pix are perfectly fine.

[ratgon]

Thanks! I'll post the schematic when I get home and thanks for all the info. And don't worry, they are safe and sound. I won't be fooling around withm them. The amp works. Sounds great. The 6L6's in there seem to be fine. By sounding great I should sayminus the noise and cracklimh. You can clearly hear a great sounding amp not too far below the noise level/

[PRR]

5881 replaces 6L6 in applications where 6L6 fail too often.

This is original-series 6L6: metal, A, B, G. The 6L6GC is a different tube, higher ratings than 5881, though a golden-age 5881 is probably the tougher tube within its ratings.

Yes, all you should do with that amp is adapt a guitar plug. And fix whatever has gone bad in 70 years. Maybe polish, maybe just preserve the patina. It is good the way it is, and it would be a shame to "soup it up".

[ratgon]

Exactly. Someone already put a guitar jack in. I simply want to recap and replaced the minimum. It sounds great as it is. And it's actually not so form factor wise ungainly to build a cabinet around. It just needs a cleaning and an overhaul. I'll work on the cabinet design first while I learn enough to handle the other aspects.