Reuse iron and parts from old tube lab equipment - Radiometer HO32

[Sesh]

EDIT: Topic has changed since original post. See latest posts.

Hi there!

I'm unsure if it's the right place to post, but I figured that's a lot of knowledge of the type I'm seeking here.
So, long story short -  I'm obsessed with the idea of repurposing old equipment as donor chassis/cabinets for my tube amp builds (perhaps tube mic pres, too). For several reasons:

1. Because my carpenting skills leave a lot to be desired (and I don't think that proces is fun).
2. Related to 1. - because the good handmade DIY cabinets from even a "cheaper" vendor like the German site TubeTown cost almost as much as a second hand commercial tube amp. (Only reasonable considering it's EU wages, high quality wood etc.)
3. The possible low-end "donor cabinets" (A Fender Frontman or what have you) are too low quality, too generic, shiny and new - I love gear with character and history, dings, scratches, warts and all.

But being an ignorant millenial, I want to cover my blind spots and show respect for history, i.e. I don't want to use equipment that has potential (historic, personal/collector) value or can still be used. But it's super hard to navigate, when you don't know how this stuff is used/used to be used.

I'm personally in love with the look of old tube radios/stereos and lab equipment. The raw steel cases and the big chunky bakelite knobs or the wooden art deco-style cabinets in odd shapes. A lot of it seems to be collecting dust in the local classifieds, with some costing next to nothing and still having been for sale for a year, sometimes several. So as I see it, I'm stopping it from becoming landfill. Some of them even has some tubes usable in guitar amp circuits and thus might have power transformers that are usable.

What is your take? Anyone tried something similar?

[tubenit]

Not sure exactly what you're asking?  Can you be more specific with the question, please?


With respect, Tubenit

[Latole]

Some carpenter in you town can built amp cabinet for cheap.

You have to provide plans and tolex covering by yourself.

[mresistor]

Plenty of folks have converted old radios or public address amplifiers into a guitar amplifier. It's not difficult but it requires skills, planning and good implementation. For instance a Bogen like this https://www.ebay.com/itm/154623137962?hash=item240041d8aa:g:jLQAAOSwtuFhTJXB.  However as you can see some of these old tube amps are not cheap anymore and you will
be lucky to find one that is.  Many people here have converted Hammond and other organ chassis into guitar amplifiers and made the cabinets for them too. Cabinet making may not always be fun
but in the end it is a rewarding experience.  Latole's suggestion is a good one, talk around town and find a person who is good with woodworking and willing to make a cab for you.
I don't know where you are other than Europe, so it's up to you to find the donor amp and then post your questions about it.  Some have come here asking if a particular old amp and transformers
are suitable for use to build a guitar amp, and since their questions are item specific they can be answered.


Guess the answer for you is yes it can be done.  Is it easier than just finding a chassis and building a new amp? Maybe and maybe not. Is it less expensive? If you can find usable transformers for cheap it would probably be less expensive. 


( I have no idea why the paragraph gets chopped up like that when you go back and add one word in edit mode)

[Sesh]

Sorry, I was obviously too vague. Forget about my cheapness, it's not the deciding factor (though it is a factor).
Thing is, I have a soft-spot for oddball, weird-looking gear and off-brands. Instead of a Fender Twin, I have a Gretsch 6163, instead of a Marshall, I have a Selmer Treble & Bass Mark II. You get the idea, I hope.

So I don't want a generic cabinet, even if it's great quality made by a great local carpenter. I want something with history, because those kind of aesthetics inspire me.

My question is then: Is it bad taste to repurpose something with potential historic value - something that collectors somewhere would want?

Let me give an example:
I've eyed a piece of old tube lab equipment - a Radiometer Beat Frequency Oscillator HO32:
https://www.radiomuseum.org/r/radiometer_signal_generator_ho_32_c.html#
I absolutely love the aesthetic and I'd reuse stuff like pilot light, switches, bakelite knobs. And it's got an EL84 output in there (tho no output transformer as far as I can tell from the schematic), so I might be able to use the PT for a scratch build - like I intend to. Plenty of space for a turretboard or something in there if I clear it out.

My first thought: This equipment is obviously obsolete, it being tube and all. Heck, from what I read its function is obsolete, too.
But then.. I don't want to be, as I said somewhat self-ironically, an ignorant millenial ruining beautiful relics of the past for my own aesthetic pleasure. A true collector might want it in it's original state - it's after all a rare local, Danish piece.

So I'm kind of torn. The same principles go for some tube radios and reel to reels I've looked at, some of them containing (potentially) usable iron, too. I know too little of the "collector's culture" around these items.

EDIT: Mr. D-Lab knows what it's about:

[HotBluePlates]

... I'm obsessed with the idea of repurposing ...

Give it a shot.

I think you'll find the process seemed better in your imagination than it turns out when you actually try it.

[thetragichero]

rule of thumb is see if it has value on ebay/etc (based on sold listings, not optimistic buy-it-now pricing... i routinely pick up hammond a100 series organs for the price of "i won't charge you to haul it away from your house" while there are some listed on reverb for over a grand) before gutting it for an amp. test equipment is fair game (especially if they contain nixie tubes and you want to get creative with them). radios and reel-to-reel are a bit murkier

that all being said, my first cabinet and headshell i absolutely loathed woodworking. took about a week to make a 2x12 and there's way more bracing than it would ever need. but what i learned from the first few helped make each subsequent build going forward easier. butt joints with titebond iii and hardwood dowels are a lot less fussy than fancy joinery and pretty rock solid. all that is really required is good square cuts (miter saw). belt sander or spoke shave to smooth out any overlap. router table to round off the edges (spent more for a set of cheap bits than i did on my $25 pawn shop router table). tolex is still aggravating but i've come to enjoy making sawdust. dimensional pine or ply (i usually get hardwood-faced pine ply, although i have used scraps of subfloor for builds before and they aren't too bad after filling voids. birch ply is too pricey for me) is relatively cheap. get a ton of clamps (don't forget 8 right angle corner clamps). there's something about creating a 3 dimensional useful object out of flat stock that is incredibly satisfying

[thetragichero]

Give it a shot.

I think you'll find the process seemed better in your imagination than it turns out when you actually try it.

i often discover that the engineers who crammed all that stuff into the chassis were a lot smarter than i am

[Sesh]

Give it a shot.

I think you'll find the process seemed better in your imagination than it turns out when you actually try it.

i often discover that the engineers who crammed all that stuff into the chassis were a lot smarter than i am

But... in most cases there are lots of space? I should clarify only be scratch building single-channel studio-sized amps or simple microphone preamps like an RCA BA-2C. Not using the existing electronics.
In the Radiometer HO32 there's more than enough space for, say, a small single-ended amplifier.

In some cases I'd also only use the chassis and the cabinet (with no speaker), some of which are huge. Like some tube radios with built-in speakers.

My ethical doubts are all about if I'm destroying these items by clearing out all the unique electro-mechanical pieces and whatnot - stuff that can't be recreated today. I'm thinking about offering them for free to someone who can use them after taking them out, tho.

[Sesh]

rule of thumb is see if it has value on ebay/etc (based on sold listings, not optimistic buy-it-now pricing... i routinely pick up hammond a100 series organs for the price of "i won't charge you to haul it away from your house" while there are some listed on reverb for over a grand) before gutting it for an amp. test equipment is fair game (especially if they contain nixie tubes and you want to get creative with them). radios and reel-to-reel are a bit murkier

that all being said, my first cabinet and headshell i absolutely loathed woodworking. took about a week to make a 2x12 and there's way more bracing than it would ever need. but what i learned from the first few helped make each subsequent build going forward easier. butt joints with titebond iii and hardwood dowels are a lot less fussy than fancy joinery and pretty rock solid. all that is really required is good square cuts (miter saw). belt sander or spoke shave to smooth out any overlap. router table to round off the edges (spent more for a set of cheap bits than i did on my $25 pawn shop router table). tolex is still aggravating but i've come to enjoy making sawdust. dimensional pine or ply (i usually get hardwood-faced pine ply, although i have used scraps of subfloor for builds before and they aren't too bad after filling voids. birch ply is too pricey for me) is relatively cheap. get a ton of clamps (don't forget 8 right angle corner clamps). there's something about creating a 3 dimensional useful object out of flat stock that is incredibly satisfying

That sounds great, and I can fully imagine that! But as I see it, that adds another hobby to the list, haha. New tools to be bought, YouTube tutorials to be watched, sites to be read.
My hobby here is primarily gear building - it also counts guitarpedals, microphones (mostly mods), modular synthesizers, guitar tube amps, outboard. Hence my desire to reuse existing stuff :)

[sluckey]

I've repurposed quite a few Hammond organ amps, radios, R to R, even a toaster oven!

     http://sluckeyamps.com/smoky/smoky.htm
     http://sluckeyamps.com/RCA/RCA.htm

Follow the link at the bottom of those pages to see even more oddballs.

[Sesh]

I've repurposed quite a few Hammond organ amps, radios, R to R, even a toaster oven!

     http://sluckeyamps.com/smoky/smoky.htm
     http://sluckeyamps.com/RCA/RCA.htm

Follow the link at the bottom of those pages to see even more oddballs.

Inspiring stuff! That's exactly what I'm talking about. Beautiful.
But I read that your stuff was beyond restoration. That's not the case in some of the things that I'm looking at.

Oh well. I think should stop overthinking it and just try it like someone here said. If I use it, the history of the unit survives in a way. Especially if the seller is unsuccesful in selling it and it ends up at the dump.

I'm gonna have to read up on how to test and reuse power transformers from old gear in new builds. I know there's some considerations around current and voltage. Any resources you would recommend?

[Sesh]

OK! So I dropped my lofty ethical ideals and just said f*** it. Changed the topic.
I bought the Radiometer tube Beat Frequency Oscillator (Type HO32).

If all else fails as an über cool headcab+chassis for a small amp.

Still waiting for it to arrive.. in the meantime, I'm interested in what I can gather from the schematic and specs. The former owner said "it works", for what that's worth.

Here's the schematic:
http://peel.dk/Radiometer/pdf/HO32%20%28Beat-frequency%20oscillator%29.pdf

The circuit powers several tubes, including an EL84. Stock it's diode rectified with a PT with 300v and 80ma for the plates plus a heater wire with 1,4 A.
That should be great for a guitar amp, right?

It also has what I believe is an output transformer?


Am I right? And will it fit output tubes and speakers?

[PRR]

It IS of course an audio power amplifier, 3 or 4 Watts. The 5Ω tap will work OK for most speakers.

A 1V (hi-fi or preamped) signal at Ampl. Input will make full output _IF_ you can figure out the switching. Some of those switch positions won't make the full 4 Watts because it is attenuated; handy when the baby is sleeping. Some may be too soft to hear?

If you go in and disconnect the CLCLCLC filter and put an input jack there, the magic eye will dance too.

No arm is strong enough for a full set of 1 Volt from e-guitar. The best fix is a preamp, one stage may be plenty, one of the oscillators might be repurposed. The snip-fix is to disconnect the negative feedback at "NFB".

[Sesh]

It IS of course an audio power amplifier, 3 or 4 Watts. The 5Ω tap will work OK for most speakers.

A 1V (hi-fi or preamped) signal at Ampl. Input will make full output _IF_ you can figure out the switching. Some of those switch positions won't make the full 4 Watts because it is attenuated; handy when the baby is sleeping. Some may be too soft to hear?

If you go in and disconnect the CLCLCLC filter and put an input jack there, the magic eye will dance too.

No arm is strong enough for a full set of 1 Volt from e-guitar. The best fix is a preamp, one stage may be plenty, one of the oscillators might be repurposed. The snip-fix is to disconnect the negative feedback at "NFB".

Hi PRR

Thanks for the advice. I'm sorry I wasn't clear enough/used the wrong terminology in the topic.
What I meant was not "repurpose" per se, but rather reusing as many parts as possible in a scratch build.

So I was wondering what kind of typology/circuit the transformers lend themselves to.
With the single EL84 the PT is built for, I thought about building a single-ended Selmer (Little Giant, Corvette etc.) or one of the single 6BQ5 Gibsons (GA-5) from the iron. But don't know if the specific OT can handle that.

[sluckey]

That PT and OT are working fine with an EL84 as is. Should work fine in any small SE EL84 amp.

[PRR]

I think it is beautifully built as-is. Limit your creativity to a preamp stage and tone controls.

No, we've never found a good audio use for the big variable caps in radios and oscillators.