Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on December 06, 2025, 04:22:29 am
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Hey guys,
I have the pleasure to restore one of these.
(https://i.imgur.com/elEvy6z.jpg)
(https://i.imgur.com/Ny8fDFY.jpg)
(https://i.imgur.com/oOle2jQ.jpg)
(https://i.imgur.com/21vmwZP.jpg)
(https://i.imgur.com/dTffHUa.jpg)
(https://i.imgur.com/K2yCY5m.jpg)
(https://i.imgur.com/1yzuymZ.jpg)
(https://i.imgur.com/vuFApru.jpg)
(https://i.imgur.com/kGpU7BR.jpg)
(https://i.imgur.com/viKbbrU.jpg)
(https://i.imgur.com/eplUFsE.jpg)
(https://i.imgur.com/DfXAP9D.jpg)
I'll be looking for some guidance on how much I'll need to remove and replace to keep it as original and safe to use
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Hi Timbo,
She's had a bit of a caning! :laugh:
I always fit the Hammond Transformer into them (in my travels in Canberra area they usually come with the 115V tranny and a second Stepdowm 240:115V Typical around120VA)
Can Electro would be suspect and I replace the first 2 Power resistors (Node 2 and 3) with Metal Oxides ( 2 or 3W) You can see charring on one already.
For the Chassis solder points I recommend a 150-180W soldering iron and a good flux (clean off the residue).
I haven't really done any serious chassis restoration, so somebody else my want to chip in.
Hope you have a bit of time free over Christmas.
All the best and it should come out really nice. In my opinion, they are a sweet little amp with a bit of character.
Kind Regards
Mirek
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Thanks mate,
I think I'll totally dismantle the chassis so I can give it a good clean and work back from there.
I'm not 100% sure of the story of this amp, I'm assuming that the original PT was to be replaced with the Ferguson PT166 325-0-325 @60mAs
and Hammond PT was also purchased as it was a better vintage look.
FENDER.PDF (https://el34world.com/charts/Schematics/files/Fender/Fender_vibro_champ_aa764.pdf)
The original schematic calls for 315-0-315 HT so I guess the 325-0-325 will have to be close enough
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Jealous. I saw one at Pete's music shop in King Street, Newtown last time I was in Sydney, but didn't have the spondoolies to collect it at the time.
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Chassis stripped
(https://i.imgur.com/pszbzOs.jpg)
(https://i.imgur.com/na0D7YY.jpg[/img
https://i.imgur.com/WK1acHD.jpg
https://i.imgur.com/sCxvSDW.jpg
And cleaned
https://i.imgur.com/vtUm6pS.jpg
https://i.imgur.com/SvIzdSh.jpg
https://i.imgur.com/bsHHpif.jpg)
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And cleaned
(https://i.imgur.com/bsHHpif.jpg)
(https://i.imgur.com/vtUm6pS.jpg)
(https://i.imgur.com/SvIzdSh.jpg)
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where you riding a Horse with no name when you stumbled on that Sun-baked beauty??
speaking of Sun, it's about time you give it a push back across the equator, bite chilly n dark up Norte'
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Amp looks like it was left out on the front porch in Florida for a year. That's going to be a lot of work - good luck!
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I have a personal 67 Vibro Champ, wasn't as bad as the one you have. I made the decision to replace all the guts with new modern film resistors and metal oxide power R's and updated caps. Sounds fantastic, kept all stock values but that tiny OT at 5 watts does contribute to the amps tone but I had an old 8 watt paper wound SE OT laying around, installed it. The Amp still has the original tone but just a little more clean headroom. The new OT was perfect for 8 ohms too. I took the original baffle bd with the 4 ohm speaker out and replaced it with a Jensen alnico 10" 8 ohm speaker and new baffle bd, grill cloth. I kept the original baffle with the original grill cloth and spk. I didn't butcher the amp, I can easily but it pack to stock, but the old R's and caps are gone, most were toast, kept original PT.
So, might not be an original component Vibro Champ but the OT and baffle can easily be put back, close enough. I guess it depends on the owners choice what to keep or replace but those components look pretty unreliable. Keeps us posted.
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Hey guys,
The process to rebuild starts
(https://i.imgur.com/8iBylTq.jpg)
The RCS's are a bit beyond help, and a reverb tank offered these.
(https://i.imgur.com/H5ZNoYa.jpg)
(https://i.imgur.com/TwXfV9j.jpg)
The sockets are in good condition after a clean, tested for grip on the pins and alls good.
New lead and lead retention installed
The OT may or may not be showing signs of overheating as there was a little wax oozing from under the bel end
Continuity tested good and turns ratio has it at 9K primary, maybe a little high??
(https://i.imgur.com/YVDmByY.jpg)
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Hey guys, It's all coming together nicely.
The original speaker is 3.2ohms and I multiplied the turns by 4ohms this is why I got a higher primary, multiply it by 3.2ohms and much closer to 8K primary.
(https://i.imgur.com/Oer4qvL.jpg)
New heater wiring with an artificial CT to the 6V6 cathode.
New 250v/3A slide switch
New PT installed.
A quick check of voltages ATM and all presenting as they should
(https://i.imgur.com/Yoj5orL.jpg)
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The circuit board/pots cleaned
New electrolytics installed
I checked all resistors and they were close enough to marked values
The caps were a bit all over the place, these I'll just wait and see what they do.
The two dropping resistors measure close to their value, so they will stay in for now.
Had a vintage looking resistor to replace the 470ohm 6V6 cathode resistor.
Circuit board reinstalled and wires connected.
(https://i.imgur.com/anSEE5O.jpg)
(https://i.imgur.com/scB4s9f.jpg)
(https://i.imgur.com/YcM2Al5.jpg)
Waiting for the delivery of the remaining parts