My Jet City JCA50H — supposedly a clone or really close to the Soldano Hot Rod Plus — has a bulging Junzl HP capacitor so I'm recapping it. I have noticed the bias circuit diode is covered with the glue used to stick the capacitor to the board in the assembly process.
I'm worried this glue may be conductive or turn corrosive with time, so I'm considering to replace it too. I can't find the reference of the installed diode, would a 1N4007 be adequate? any characteristic to look for or just 1N4007 from a reliable manufacturer and provider should be ok?
Would be a good idea to replace bridge rectifier diodes with UF5408 for reliability or it may cause trouble? I'll probably leave it as is, but I'd like to know if I ever have to replace them.
Replacing diodes in Jet City JCA50H
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Stevem
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Re: Replacing diodes in Jet City JCA50H
Your fretting over nothing in my opinion.
If your looking for something to spend time and maybe some money on then critiquing / auditioning a few different first preamp tubes is what I would do.
The first gain stage tube sets up the whole tonal nature and gain feel of the amp since what it does only gets amplified on down stream thru the amp.
If this first preamp tube isn’t as much to your liking as it can be then your beating your head against the wall making mod’s to the rest of the amp other then optimizing the speaker(s) to your liking.
Also electrolytic cap wise I deal with failed modern caps all the time in both SS and tube gear and there failure can 98% of the time be traced to them being run too close to there stated voltage, as in the amp being built to a price point and penny pinching being employed.
If your looking for something to spend time and maybe some money on then critiquing / auditioning a few different first preamp tubes is what I would do.
The first gain stage tube sets up the whole tonal nature and gain feel of the amp since what it does only gets amplified on down stream thru the amp.
If this first preamp tube isn’t as much to your liking as it can be then your beating your head against the wall making mod’s to the rest of the amp other then optimizing the speaker(s) to your liking.
Also electrolytic cap wise I deal with failed modern caps all the time in both SS and tube gear and there failure can 98% of the time be traced to them being run too close to there stated voltage, as in the amp being built to a price point and penny pinching being employed.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Replacing diodes in Jet City JCA50H
I generally agree with Stevem's comments, although there are some minor bits that I would extend on.
There's nothing really wrong with putting a 1N4007 in for the bias rectifier, it's just likely to be unnecessary as Stevem says. There is no tone magic there, only it needing to make a DC voltage.
If the adhesive is hot glue, it probably will never go conductive. Conductive goop might happen with some acetic-acid curing silicone rubbers though. If you're already messing with that area, you might be able to just peel it off. If you've had the amp for some time, a year or more, it's unlikely to cause issues if it hasn't already done so.
I glanced at the schematic. If I got the correct one, those four diodes are not a bridge rectifier - they're two diodes in series on each side of a Full Wave Center Tap setup. If you just want to mess about with diodes, UF5408s would be fine. But they're more a cure for rectifier-induced hum than being necessary. The UF prefix means they won't shock the wiring inductance/capcitance resonances and make RF squarks at 2x line frequency as they turn off. Some amps have this issue with ordinary non-fast-non-soft diodes, some don't.
There's nothing really wrong with putting a 1N4007 in for the bias rectifier, it's just likely to be unnecessary as Stevem says. There is no tone magic there, only it needing to make a DC voltage.
If the adhesive is hot glue, it probably will never go conductive. Conductive goop might happen with some acetic-acid curing silicone rubbers though. If you're already messing with that area, you might be able to just peel it off. If you've had the amp for some time, a year or more, it's unlikely to cause issues if it hasn't already done so.
I glanced at the schematic. If I got the correct one, those four diodes are not a bridge rectifier - they're two diodes in series on each side of a Full Wave Center Tap setup. If you just want to mess about with diodes, UF5408s would be fine. But they're more a cure for rectifier-induced hum than being necessary. The UF prefix means they won't shock the wiring inductance/capcitance resonances and make RF squarks at 2x line frequency as they turn off. Some amps have this issue with ordinary non-fast-non-soft diodes, some don't.
"For every complex problem there is an answer that is clear, simple, and wrong"
H. L. Mencken
H. L. Mencken
Re: Replacing diodes in Jet City JCA50H
Thank you for your insights.
If the glue is not a problem then I'll leave it as is. I don't pretend to change or improve the amp's tone through modding, but since I actually have access to the PCB solder side I was considering to install good quality diodes to improve its reliability. But I'll stick to "If ain't broke don't fix it" in this case.
If the glue is not a problem then I'll leave it as is. I don't pretend to change or improve the amp's tone through modding, but since I actually have access to the PCB solder side I was considering to install good quality diodes to improve its reliability. But I'll stick to "If ain't broke don't fix it" in this case.