I'm beginning a recap on an SL-10. I know the white stripe on Blue Instrument Device caps represents the positive lead unlike conventional markings. What about the caps wrapped in black with a Threshold logo? Does the "Threshold" represent the positive or negative lead?
I have not pulled the PCB yet. It looks a little tricky to trace since this is the power supply regulation circuitry and I have 4 caps on each side in opposite orientation. I think I'd need to trace them back to the 7815 or 7915 to determine polarity.
I was hoping someone had done this already and could spare me the hassle!
Thanks,
Eric M.
I have not pulled the PCB yet. It looks a little tricky to trace since this is the power supply regulation circuitry and I have 4 caps on each side in opposite orientation. I think I'd need to trace them back to the 7815 or 7915 to determine polarity.
I was hoping someone had done this already and could spare me the hassle!
Thanks,
Eric M.
The absolute sure-fire way would be to power it up and measure the voltage on the cap pins.
You may get advise here that might or might not be accurate ;-)
Jan
You may get advise here that might or might not be accurate ;-)
Jan
You guys might be right. I posted late ..... I was being lazy!!
Still, I'm sure there are a handful of folks here who have gone through the same thing. I see those black Threshold caps in all sorts of Threshold gear. What did they find? Threshold stripe positive or negative?
Still, I'm sure there are a handful of folks here who have gone through the same thing. I see those black Threshold caps in all sorts of Threshold gear. What did they find? Threshold stripe positive or negative?
The stripes correspond with whatever you measure them to be when you do what Jan and Aleks suggested.
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🙂 🙂 🙂
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🙂 🙂 🙂
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I would measure all of them and mark the pcb accordingly. The logo might not indicate the polarity at all.
Instead, the polarity could be indicated by a red dot (or a black dot) on the bottom of the capacitor
near one terminal. This was not unusual at one time. Check the bottom of one and see.
In any event, I would turn the board upside down, power it up, put your DVM leads across each capacitor,
and mark each positive voltage terminal with a red marker. Or each negative voltage terminal with a black marker.
Your choice.
Instead, the polarity could be indicated by a red dot (or a black dot) on the bottom of the capacitor
near one terminal. This was not unusual at one time. Check the bottom of one and see.
In any event, I would turn the board upside down, power it up, put your DVM leads across each capacitor,
and mark each positive voltage terminal with a red marker. Or each negative voltage terminal with a black marker.
Your choice.
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I can't imagine all the discussions and use of bandwidth for something that can be checked in about 200 milliseconds.
Jan
Jan
You're right. I did a take off last night and have the parts on order. I didn't want to take the unit apart until parts arrived but was curious if anyone had an answer. I had assumed Threshold had the wrap oriented in such a way to indicate the pos. and neg. sides (Much like Instrument Device had done). Raymas suggestion of a red dot on the underside is a possibility.
Bottom line, someone who has done an SL-10 recap is going to see this and answer the question. OR, the parts will arrive and I'll look for that dot and test polarity and post up the answer for all wanting to do an SL-10 recap in the future.
Recaping will only lower its value. No longer original, tampered with, stay away!
If it's not broken, do not touch it.
If it's not broken, do not touch it.
I deal with a lot of vintage JBL gear. There is a group of "collectors" (That's what I'll call this group) that wants the gear as original as possible. Speakers with the old Lansaloy surrounds. These become hard as rocks with age, restricts the speaker cone movement and makes a 15" woofer sound like a 5" midrange. Then you have the other group, the "audiophiles" (Yes, I would not consider vintage JBL gear something an audiophile would covet, but you get the idea). These folks want the gear to sound as good as it can or how it should when it left the factory.
I think there are more interested in Threshold gear for it's sonic capabilities and not so much as a collectors item. Atleast, that's where I am. If I keep the SL-10 all original, I'll end up putting it on a shelf and then going out and buying a different preamp to listen too.... probably another SL-10 which I'll ruin with new components!
Didn't we have a similar thread that related original vintage audio gear to original muscle cars and everyone ended up posting their vintage rides? I remember a beautiful Vette. I think it was a green, 67, tri-power 427.
Jan, now I'm drooling!
There's umpteen threads here that start with 'I recapped my XYZ amp and now it no longer works/has hum/ low volume/ noisy/ etc.'.
You want to be next?
Jan
You want to be next?
Jan
Who, me?
There are umpteen threads here that claim excellent improvements after recapping amps, preamps, crossovers, etc. I think I'm a few of them.
I'm hoping to be in that second group!
The first picture I found of an SL-10 has caps showing their polarity:
Long time ago I had sl-10, then sold it on ebay. You would never guessed who bought it from me. Amar Gopal Bose!