1959 Hoffman Tube Stereo console...NOS...Amperex Tubes

angelaudio

angelaudio

Super Member
Hello fellow AudioKarmists! Hope you all find yourselves well.

I was perusing the local classifieds today when I came across a Hoffman console.

I’d never heard of the brand and so I did a quick AK search and found that another AK’er had acquired a tube Hoffman that ended up having some Amperex tubes in it. I immediately sent the sellers an email with an offer and they responded with a “yes” and the address.

I get there and the couple are very nice and tell me that they purchased this console “new” from an auction and hadn’t even turned it on. They had bought two identical consoles and were selling the “uglier” one to me.

Well I got home and immediately removed the back cover to take a peek inside and what do I find? Yup...AMPEREX tubes, made in Holland, Austria & England. Scroe!

The changer, a Garrard RC 121 mkii, even has the round paper with instructions still on it! I haven’t plugged anything in yet just to be safe, even though everything looks to be in very nice shape under the chassis.

The console itself isn’t in bad shape either and will just need some work on the finish to get it in tip top shape.

I must say I’m looking forward to hearing those EL84’s and 12AX7’s but the only problem is I don’t have a variac so I’m not sure whether or not it would be alright to just plug and play seeing as how all the circuitry, caps in particular, look to be aesthetically perfect. If any of you folks find a Hoffman tube console for sale I’d say jump on it because you could find some nice tubes in there and you’ll probably be pleased with the iron on the chassis as well, looks formidable! Listening impressions provided after everything on the pre-launch checklist is checked off!:banana:D04F5180-15EF-4073-BB67-8F63F621FD83.jpegC6CAA8F3-8462-4F2A-A67D-A11B93CDA2A9.jpeg038EFE52-6D7B-449D-BC2C-AFBB8FA3A43C.jpegFB2D3CAC-7B42-4763-B231-F8CD338A46AD.jpeg98F6E877-520B-4EB0-9866-DFE2F8E5EE92.jpegCEFD8A33-03E7-498A-A307-738DF87ED44E.jpeg536B8F14-ECFE-41B6-84C6-9C6141A0DB16.jpeg9E518DC8-FAC8-44CB-AB7A-3C96EB28CB27.jpegE54E7C5E-D084-45A3-BB2B-EF3D5A30F402.jpeg
 
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Update: Couldn’t resist plugging it in & powering it up and...it made beautiful sweet music until I saw magic white smoke coming out from the top of power amp :eek:

I immediately shut ‘er down but damn does that smoke stink! What could have possibly been burning up in there? :dunno:
 
Prolly a dried-out electrolytic caps & cap cans, going up in smoke. Gonna need to recap all of those 'lytics and check for leaky coupling caps. I'd suggest a Variac or at least a current limiting light-bulb setup, for the post R&R fix fire-up. Just to check ramp-up voltages and possible shorts.

Good luck! Looks like a quality unit. Worthy of a good R&R. :)
 
Mr Boochie said:
Prolly a dried-out electrolytic caps & cap cans, going up in smoke. Gonna need to recap all of those 'lytics and check for leaky coupling caps. I'd suggest a Variac or at least a current limiting light-bulb setup, for the post R&R fix fire-up. Just to check ramp-up voltages and possible shorts.

Good luck! Looks like a quality unit. Worthy of a good R&R. :)
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Thanks for the info Mr. Boochie! I went back in the garage to pull the chassis after my update and made some interesting observations:
1) one of the two can capacitors was Hot
2) power transformer was hot
3) one side of one output transformer was hot
4) lots of white powdery looking stuff on the leads coming from the power transformer
5) a resistor that looks like it got so hot that one of the color bands (silver) bubbles

Hope I didn’t do any major damage to any components. I’m going to build a dim bulb tester and read some posts on how to use it. I’m still learning how to work on tube amps and from what I’ve researched on other ak posts, it seems like I might have to outline some diagnostic procedures to make sure I know exactly what needs to be done, aside from the ‘lytics and such.:confused:
 
Cap probably shorted.

I have the same guts. Its got nice transformers. Ended up bypassing the tone controls because they sounded awful. I've been meaning to try re-installing them but using the values from the official Mullard 5-10 schematic to see if it works better. The speakers in the cabinet left much to be desired too. The crossover cap lives inside the power amp, its that big 1.0 uf cap attached to the speaker output jack. I ended up swapping the woofers for a matched pair since the woofer in the main and aux cabinets were not actually the same. The midranges got swapped for some 4" midbass drivers, and the tweeters got swapped for some Vifa domes. Crossover came from a set of Polk speakers. The stock config had very limited bass and treble, the current arrangement is much better. Its still not wall-shaking but considerably better than how it came.
 
I had a Hoffman mono amp that was similar. Power transformer was thoroughly toasted, 6CA4 was gone (zero emission), so I assume a shorted filter cap took both out. At least I saved the output transformer...
 
No fuse in stock form, so I can believe complete meltdown. The output transformer is pretty stout for an EL84 console amp too. I guess I shouldn't talk too loud, mine still has original filter caps in it.

Shame you don't still have the carcass, one of mine has a broken "tone-scope" or whatever the heck its called. The plastic bit cracked in the middle.
 
My console find had a quad of Amperex EL84s in it that test 100%+. Nice find, but I'd never power on a 1959 amp without a recap, hopefully the power transformer survived.
 
gadget73 said:
Cap probably shorted.

I have the same guts. Its got nice transformers. Ended up bypassing the tone controls because they sounded awful. I've been meaning to try re-installing them but using the values from the official Mullard 5-10 schematic to see if it works better. The speakers in the cabinet left much to be desired too. The crossover cap lives inside the power amp, its that big 1.0 uf cap attached to the speaker output jack. I ended up swapping the woofers for a matched pair since the woofer in the main and aux cabinets were not actually the same. The midranges got swapped for some 4" midbass drivers, and the tweeters got swapped for some Vifa domes. Crossover came from a set of Polk speakers. The stock config had very limited bass and treble, the current arrangement is much better. Its still not wall-shaking but considerably better than how it came.
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I hope it is just a cap that fried because I would really hate to fry any of the transformers or ruin the tubes. As far as the speakers go I don’t think I was able to get a good, thorough feel/sense of what they offer but for the few minutes that I had “Tin Pan Alley” playing they sounded fairly decent...but then again, that song probably sounds good no matter where it’s coming out of :D
 
Tom Bavis said:
I had a Hoffman mono amp that was similar. Power transformer was thoroughly toasted, 6CA4 was gone (zero emission), so I assume a shorted filter cap took both out. At least I saved the output transformer...
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Ouch! That hurts. Did you transplant the OPTto another unit?
 
Aerobat said:
My console find had a quad of Amperex EL84s in it that test 100%+. Nice find, but I'd never power on a 1959 amp without a recap, hopefully the power transformer survived.
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Nice find on your part as well. Did you keep the console intact? Curiosity got the best of me, I know it wasn’t a wise decision. The amp was still playing after the smoke came out so I’m hoping that’s an indication of the PT still being good but that’s just an assumption. I’m definitely going to do a full recap on this one, but before I do how can I make sure the PT & OT’s are still good?
 
angelaudio said:
Nice find on your part as well. Did you keep the console intact? Curiosity got the best of me, I know it wasn’t a wise decision. The amp was still playing after the smoke came out so I’m hoping that’s an indication of the PT still being good but that’s just an assumption. I’m definitely going to do a full recap on this one, but before I do how can I make sure the PT & OT’s are still good?
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No, it was an unattractive French Provincial style so I parted it out, plus the amp sounds so good it needs to be in a modern system. You can check the continuity of the transformer windings.
 
angelaudio said:
Update: Couldn’t resist plugging it in & powering it up and...it made beautiful sweet music until I saw magic white smoke coming out from the top of power amp :eek:

I immediately shut ‘er down but damn does that smoke stink! What could have possibly been burning up in there? :dunno:
Click to expand...
Ouch.

What's the model number? . . . chassis number? . . . any other similar info?
 
assuming its the same as mine. Scans from the schematic pasted inside the cabinet.
 

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The best tubes in the world aren’t going to help an amp with circuit or transformer shortcomings.

If the OP is going to repair the amp I’d suggest to replace all those Amperex tubes with something cheap, al least until the amp is known to be in good working condition. It *is* possible to ruin a tube by running it in a malfunctioning circuit.
 
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