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Dynaco SCA 35, garbage find

I bought my first TT in 1970, a Dual 1209. Used it about five years, then bought a Michell Transcriptor. Sold that one after five years too. I'd donate a molar to have either of them back.

Jack
 
The 12 series with smaller platters were really conservatively designed. Had a 1228 I sold. It did everything well. Also sold a 1009sk that always worked perfectly. Didn't quite have the finess of the 1229 but it never disappointed.
 
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peterh said:
Congratulations for a nice find, it seems to be a factory made one.

BUT
Leave the soldering tool for a while. You have already started to loosen the pots, be careful with them. The balance pot is
unique dont destroy it!. The volume pot might need replacement, i have suitable replacements located within EU
You EL84 is most likely shot, you need a matched quad EL84 in this amp.

And i repeat, you don't need to replace caps on the boards, you _might_ need to replace out-of-tolerance resistors but
i suggest you wait with this until you have a working amp that delivers full power.
As for the electrolytics , install EFB instead, there is ready made kits for this.
Click to expand...
Hej Peterh,
many thanks for your advise, with some WD40 and carefully with pliers I managed to save the volume, balance and bass pots and all 3 are now in working condition, but I managed to destroy the treble pot (my bad), I normally like to have flat tone controls so I can live without treble pot.
I see you are placed in Gothenburg and that you have replacements for volume pot, just by coincidence are you related to tubular-well.se?
Would you suggest to first replace out of tolerance resistors and then later replace the EL84s?
cheers
Victor
 
ferran39 said:
Hej Peterh,
many thanks for your advise, with some WD40 and carefully with pliers I managed to save the volume, balance and bass pots and all 3 are now in working condition, but I managed to destroy the treble pot (my bad), I normally like to have flat tone controls so I can live without treble pot.
I see you are placed in Gothenburg and that you have replacements for volume pot, just by coincidence are you related to tubular-well.se?
Would you suggest to first replace out of tolerance resistors and then later replace the EL84s?
cheers
Victor
Click to expand...
Victor,

I Am tubular-well.se :)

I recommend to start with EL84, and keep the soldering tool resting. Those boards are fragile and the design is tolerant against component variances. Better to keep calm and install new boards if and when you decide to keep the amp.
The EL84 is hard pressed and will need replacements, the ECC83 and 7199 is most likely ok.
( a persistent hum could be the first sign of a 7199 needing replacement, those are hard-to-find and expensive thus
it might be better to replace the boards to new ones that uses alternative to 7199 s.a. ecf80/ecf82)
 
peterh said:
Victor,

I Am tubular-well.se :)

I recommend to start with EL84, and keep the soldering tool resting. Those boards are fragile and the design is tolerant against component variances. Better to keep calm and install new boards if and when you decide to keep the amp.
The EL84 is hard pressed and will need replacements, the ECC83 and 7199 is most likely ok.
( a persistent hum could be the first sign of a 7199 needing replacement, those are hard-to-find and expensive thus
it might be better to replace the boards to new ones that uses alternative to 7199 s.a. ecf80/ecf82)
Click to expand...
Hej Peter,
ok jag förstår, jag sitter själv i Lund ;)
since I found the amp I spotted the JJs EL84 at your website, I will wait to save the money and grab them, probably the volume pot as well.
I will keep the amp and eventually replace the boards, etc. but I see it as a long term project.
many thanks for your advises
 
I've had some luck holding a soldering iron to the threaded bushing on pots that were stuck and oil didn't free up. Some heat seems to help pull the oil in and free it up. Kind of a last-ditch effort but if its not working already there isn't much to lose.
 
ferran39 said:
Hej Peter,
ok jag förstår, jag sitter själv i Lund ;)
since I found the amp I spotted the JJs EL84 at your website, I will wait to save the money and grab them, probably the volume pot as well.
I will keep the amp and eventually replace the boards, etc. but I see it as a long term project.
many thanks for your advises
Click to expand...
I must ask : where did you find this treasure ?
 
gadget73 said:
I've had some luck holding a soldering iron to the threaded bushing on pots that were stuck and oil didn't free up. Some heat seems to help pull the oil in and free it up. Kind of a last-ditch effort but if its not working already there isn't much to lose.
Click to expand...
thanks gadget73, I salvaged the pots with little WD-40 and carefully turning with pliers
 
Hey guys,
I´m back with an update on this one, the amp has been sitting for a while due to some hum/noise issues.
-Now I have installed a new replacement for the destroyed treble control pot, and I found a couple of bad solderings (points 6 & 7 on the left channel board), after re-soldering voila the major hum issues are gone.
-I installed a headphone jack according to the manual with a 100 ohm resistor for each channel, while listening with headphones I noticed a minor hum and noises that come and disappear, I swapped tubes positions and found that the hum issue follows one of the 7199, it seems that the 7199 must be replaced.
Since the 7199 are hard to find, it seems that a replacement can be 6U8a or ECF82 with an adapter. I found some ECF82 Yugoslavia at a good price for a matched pair.
A pair of questions for you guys: will the ECF82 work fine or should I get 6U8a? do they have to be matched?
-As the light diffuser was missing since I found the amp, I had tested some replacements and the winner was a little LEGO round brick

the amp with replaced treble pot, and headphones jack

DynacoSCA35_10.jpg

the LEGO brick as light diffuser, the faceplate has been cleaned and polished knobs

DynacoSCA35_11.jpg

a just for fun test with a customized light diffuser

DynacoSCA35_12.jpg
 
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I have found quite a few 7199's that have a bit of hum. What I have found, that has always worked, was to lift the filament voltage above ground by 25-50v. I do this by creating a 25-50v supply line. I make a 1-10 voltage divider from the high voltage power supply, and I find it necessary to bypass that with a small film cap, otherwise it has a high pitched buzz. This has cured every 7199 I have tried it on.
 
billyz said:
I have found quite a few 7199's that have a bit of hum. What I have found, that has always worked, was to lift the filament voltage above ground by 25-50v. I do this by creating a 25-50v supply line. I make a 1-10 voltage divider from the high voltage power supply, and I find it necessary to bypass that with a small film cap, otherwise it has a high pitched buzz. This has cured every 7199 I have tried it on.
Click to expand...
I elevate the AC filaments in all new builds now as a matter of routine. None so far have required any additional measures for hum control.

Jack
 
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