Search found 177 matches

by oldmacman
Mon May 19, 2025 3:31 am
Forum: Dumble Discussion
Topic: German YouTube video -- circuit walkthrough and measurements
Replies: 4
Views: 614

German YouTube video -- circuit walkthrough and measurements

https://www.youtube.com/watch?v=TMCZQt3ghEg and the follow-on: https://www.youtube.com/watch?v=B0t6krnjvv4 Have y'all seen this? You can turn on the captions and select auto-translation to English and understand most of it. The schematic is close to the 2nd gen ODS in the files section, with a diffe...
by oldmacman
Thu Apr 03, 2025 6:02 pm
Forum: Fender Discussion
Topic: Rivera Stage 2 or 4 mods
Replies: 2
Views: 848

Re: Rivera Stage 2 or 4 mods

There is some info here: https://www.thegearpage.net/board/index.php?threads/paul-rivera-mod-for-steve-lukathers-deluxe-reverb-video.1828908/ Specifically, it looks like he put a switchable 220K resistor across the 3M3 reverb mix resistor for a gain boost, and added a switchable set of capacitors in...
by oldmacman
Wed Mar 26, 2025 2:28 am
Forum: Dumble Discussion
Topic: Getting plate voltages just right?
Replies: 13
Views: 5785

Re: Getting plate voltages just right?

Do you have the FET input installed? If not, an additional dropping resistor at the end of the string might bring the voltages down a hair to where you want them to be.
by oldmacman
Sat Mar 22, 2025 12:03 am
Forum: Dumble Files
Topic: OD-50W #0049 (Cesar Diaz schematic)
Replies: 0
Views: 1416

OD-50W #0049 (Cesar Diaz schematic)

Going back through my collection of files, somebody sent this to me in 2005, not sure who, but I haven't seen it posted here before. My understanding is that this is the schematic that was digitized (with a lot of errors) as '70s ODS on Schematic Heaven back in the day. The voltages and the general ...
by oldmacman
Fri Mar 21, 2025 4:33 pm
Forum: Dumble Discussion
Topic: ODS #020 for sale on Reverb
Replies: 26
Views: 23667

Re: ODS #020 for sale on Reverb

Here is some more information that I got from a forum member almost 20 years ago. Since then, the amp has been sold a couple of times, and a gut shot and most of the values ( https://ampgarage.com/forum/viewtopic.php?f=4&t=33286 ) have been posted here already, so I’m going to go ahead and share wha...
by oldmacman
Thu Feb 13, 2025 7:11 pm
Forum: Dumble Discussion
Topic: Early Peavey tonestack same as Dumble?
Replies: 1
Views: 1296

Early Peavey tonestack same as Dumble?

I happened to run across a Reddit post this morning where somebody picked up an old Peavey Standard 260 amp from an antique store. Curious, I looked up the schematic (https://assets.peavey.com/literature/manuals/standard.pdf) and found that the tonestack looks just like an ODS -- based on a blackfac...
by oldmacman
Mon Nov 16, 2020 4:04 am
Forum: Technical Discussion
Topic: Help troubleshooting hum/buzz in Ampeg GV-15
Replies: 4
Views: 1041

Re: Help troubleshooting hum/buzz in Ampeg GV-15

It ended up being the input grounds, but in a different way than I had thought. They were all solid, with a star washer. But the grounding of the aluminum front panel to the steel chassis was not good -- it had oxidized and developed some resistance. So I took the front panel off, sanded the mating ...
by oldmacman
Sun Nov 15, 2020 11:00 pm
Forum: Technical Discussion
Topic: Help troubleshooting hum/buzz in Ampeg GV-15
Replies: 4
Views: 1041

Help troubleshooting hum/buzz in Ampeg GV-15

Hi all, A while back, I got an old Ampeg GV-15 chassis for cheap, not working. The power and output transformers had been replaced, and the amp was in pretty bad shape, with rust and nicotine stains all over. I cleaned it up and replaced the electrolytic caps and a couple of bad resistors, and it's ...
by oldmacman
Wed May 15, 2019 1:50 am
Forum: Technical Discussion
Topic: ECF82 / 6U8 substitutes EF86 + PI triode?
Replies: 10
Views: 4341

Re: ECF82 / 6U8 substitutes EF86 + PI triode?

Check out how the Standel 50L15 / S-80 uses one of these: gain stage + cathodyne PI.
standel_s80_schematic.jpg
by oldmacman
Thu May 02, 2019 1:01 am
Forum: Technical Discussion
Topic: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?
Replies: 7
Views: 3085

Re: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?

And a few of the non-trem version:
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by oldmacman
Thu May 02, 2019 12:58 am
Forum: Technical Discussion
Topic: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?
Replies: 7
Views: 3085

Re: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?

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by oldmacman
Thu May 02, 2019 12:57 am
Forum: Technical Discussion
Topic: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?
Replies: 7
Views: 3085

Re: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?

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by oldmacman
Thu May 02, 2019 12:54 am
Forum: Technical Discussion
Topic: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?
Replies: 7
Views: 3085

Re: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?

Here are a few sets of photos from Reverb listings, Instagram, etc. 20837330_136109086994566_2982582310051774464_n.jpg 20766572_2195543070692575_8472337433952780288_n.jpg 20766352_1906567629591003_830828193249230848_n.jpg 20766138_287991248345768_8964549400563023872_n.jpg 20759940_110687016278551_91...
by oldmacman
Thu May 02, 2019 12:52 am
Forum: Technical Discussion
Topic: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?
Replies: 7
Views: 3085

Re: Schematic/layout for Standel 20J12 / S-50 -- help with missing values?

I was able to get some more info and detailed photos of a 20J12T to fill in the gaps. Attached are the new revisions for both tremolo and non-tremolo versions.