Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: skallywampus on August 02, 2020, 12:16:23 pm

Title: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: skallywampus on August 02, 2020, 12:16:23 pm: Looking for the reason no tremolo and a beginner at this and no schematic to help sets me back. Do any of you know of a similar schematic I may learn from?
thanks, Skallywampus
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: shooter on August 02, 2020, 12:26:55 pm: Here's Doug's schematic page, find something you like, maybe we can help start the process

https://el34world.com/charts/TubeAmpSchematics.htm
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: sluckey on August 02, 2020, 12:47:58 pm: Tell us what tubes are in it. Show us some pics of the chassis, inside guts and outside layout.

Your schematic is not complete and the input jacks are connected to ground.
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: skallywampus on August 02, 2020, 01:17:21 pm: thank you ..drawing the schematic as I go....(hurricane outside anyway...) here are some more pics. There is an ID plate x79202....
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: vampwizzard on August 02, 2020, 02:34:08 pm: Valco tonemaster? https://reverb.com/item/2032134-rare-1956-valco-tonemaster-english-electronics-twin-6l6-15-amplifier (https://reverb.com/item/2032134-rare-1956-valco-tonemaster-english-electronics-twin-6l6-15-amplifier)
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: Latole on August 02, 2020, 02:37:57 pm: https://el34world.com/Forum/index.php?topic=14581.0

http://www.oldfrets.com/Valco/Schematics.html
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: PRR on August 02, 2020, 02:57:20 pm: The LFO seems taken from Supro 1690T. The fact the audio stage is triode or pentode is probably not very important.
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: Latole on August 02, 2020, 03:05:06 pm: Often with tremolo issue and if tube is good; I replace all tremolo circuit capacitors.
It's aways work....and cost only few $
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: skallywampus on August 02, 2020, 03:56:23 pm: here's the tube layout...
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: bmccowan on August 02, 2020, 05:16:27 pm: That's a pretty rare amp. I think VampW has it right. English Electronics was one of the Chicago music stores that Valco labelled amps for. Folks, including me, have looked for that schematic before. So if you sketch out the schematic, and post pics of the guts, folks here can help you fix the tremolo, and many, me included will be happy to have the schematic.
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: ALBATROS1234 on August 03, 2020, 04:22:02 pm: yea thats a bad ass valco wouldnt mind taking a peek at its underbelly. weird how its got the 5979 mini with metal octals. ive seen a few like that with the preamp connected with the umbilical cord to the power supply/power amp. i bet it has the sweet gritty 50s valco sound too.
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: bmccowan on August 03, 2020, 08:03:09 pm: Quote
weird how its got the 5979 mini with metal octals. ive seen a few like that with the preamp connected with the umbilical cord to the power supply/power amp.
Yup on the 5879. I thought I'd be able to find a very similar earlier schematic with a 6SJ7 in that position, but I did not. I have three Valco basket cases awaiting rebuilds. Two have separate preamps with an umbilical cord, but they are clearly different circuits. Valcos are hard to work on, what with the crowded terminal strips, but they are a ton of fun and tone!
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: skallywampus on August 04, 2020, 01:58:08 pm: This is what I have for the tremolo circuit so far....no oscillation.
so...
jumped 22K on off switch.....no change.
jumped 1.5K Cathode 5879 ..no change
raised 1.5K to 3.9K on 5879...lowered volume start tremolo..not sustain
raised 1.5K on 5879 to 1meg....lowered amp volume and tremolo started and does not sustain
Paralleled 47uf cap on 5879cathode...no change
just shotgunning I guess....
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: PRR on August 04, 2020, 03:54:15 pm: > Your schematic is not complete and the input jacks are connected to ground.

Still likely errors in today's plan (cleaned and attached).

The 0.5u cap in the LFO phase-shift seems unlikely; 0.05 or 0.02 more usual.
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: vampwizzard on August 04, 2020, 09:23:44 pm: Pretty interested in getting a working schematic out of this. Keep it up!
Title: Re: recognize this Supro?....no tremelo...no schematic info on web....?
Post by: bmccowan on August 05, 2020, 06:01:34 am: One of the Gibson GA-40 Les Paul models used a 6SQ7 for the tremolo and a 5879. The portion of the circuit in the sketch look pretty darn similar. Joe Piazza drew a very clean schematic of that amp. Maybe it helps.