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October 27, 2021, 10:01:01 PM

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Amplifier Discussion / Re: 80's Era Roland JC50 blows internal fuses
« Last post by joecool85 on Today at 02:03:37 PM »
Plugging in mono 1/4" plug into stereo headphone jack expecting stereo plug?  That could cause shorts.
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The bulb is intended for testing.  It lets you apply power to the system while protecting it in case of excess current draw, which lights the bulb instead of burning up the amp.   This process does limit the mains voltage some and that is a problem for operation.   But the bulb unit is not intended for operating the amp.  Once we know the unit will work without blowing fuses, we ditch the bulb.

Then there is the variac,  if you dial it up slowly, the amp passes through unstable periods at the reduced voltage.   and with a speaker load, it won't always settle down.

You worked on the amp, fired it up, and it worked.   Then oddly you decided to fix it some more and put it back under test conditions.   The amp works, now is the time to go over it and make sure no adjustments remain to be made under real operating conditions.
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So.
Good news.
Death cap is out, three pronger in & testing for continuity. I went to test & everything functioned as normal. Then I realized that I’d mistakenly plugged directly into the variac, and not through the lamp limiter as intended. Shut down & powered up through limiter- amp did the loud hum, pass no other signal, no power light business again. Now, I’ve used this limiter with a ‘65 Super Reverb and a Univox U-1246 bass head with no problems. They each run just like they’re plugged into the wall. Not the Standel.

Is there any explaination for this? Does the limiter not allow enough current to flow to this amp in particular? If I hadn’t previously used it successfully with two other devices, I’d question my wiring.
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Amplifier Discussion / Re: 80's Era Roland JC50 blows internal fuses
« Last post by Enzo on October 26, 2021, 07:46:45 PM »
OK, so don't plug in the phones any more.  Open it up.  Is there DC voltage on the phones jack?  Is anything loose inside that an inserted phones plug could make touch something else?

Do yoi have different phones to try?
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Amplifier Discussion / 80's Era Roland JC50 blows internal fuses
« Last post by papa_bear75 on October 26, 2021, 03:34:25 PM »
I inherited the amp from my father who passed earlier this year and was excited to use it. However, I soon discovered a problem. The amp worked perfectly well until I plugged in a set of headphones. As soon as I did that, the audio in the headphones was distorted. After a couple seconds, the audio started fading. The LED on the power switch faded in sync with the audio until they were both completely off. I checked the main fuse and it was fine. I opened up the unit and found that both 4A fuses were burned. I picked up some replacements and installed them thinking the amp had a deeper issue. I powered it up and the amp worked perfectly. I proceded to plug the headphones back in and the fuses burned again. I replaced them again and tested the amp without headphones. It worked perfectly. I do live in a condo so having the ability to use headphones is key.

Is this something that anyone has encountered before?

Thanks!
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Amplifier Discussion / Re: 1970 Standel SB30 troubleshooting/ death cap identification
« Last post by g1 on October 24, 2021, 01:35:25 PM »
You are correct in that C16 would be the death cap in units equipped with the polarity switch.
But according to the notes, only the PA6 had that switch, so it should be C2 (pg.3) as loudthud stated.

Attaching schematic as the link gave me a bit of trouble as well.
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Well awright then. I’m gonna make a cap discharge tool, pluck that thing, change out the cord, test & report back.

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Amplifier Discussion / Re: Remote channel/FX switch
« Last post by Enzo on October 24, 2021, 01:02:47 AM »
Sure, there are other ways to get home.  I was addressing the OP question.  He apparently wants to design his own with these features.  I mean, how can I add a gain channel to my amp is a separate question from what pedal should I put in front of my amp.
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Amplifier Discussion / Re: 1970 Standel SB30 troubleshooting/ death cap identification
« Last post by Enzo on October 24, 2021, 12:58:35 AM »
Link worked for me, four pages.
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Amplifier Discussion / Re: Remote channel/FX switch
« Last post by phatt on October 24, 2021, 12:17:25 AM »
Switching is simple, it was his desire to have a remote reverb level control that was a challenge.

Maybe I was not clear?
Surely it would be so much simpler to use a multi FX pedal board of which there are dozens to choose from, many now for sale cheap SecHand.
A lot of those FX units have a foot control which can be assigned to FX paremeters.
Simply assign Reverb depth to the pedal and you have real time hands free control over Reverb depth.

To my understanding that makes a lot more sense than reinventing the wheel again. :loco

One way means it's dedicated to one Amp Only, the other means it's totally independent of the amplifier which means if Amp fails you swap to another amp and still keep all the FX tricks you wish to use.
Either way you still end up with a pedal on the floor. ;)
Phil.
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