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Messages - g1

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1
Amplifier Discussion / Re: Peavey Bandit as speaker cab
« on: November 18, 2021, 02:03:26 PM »
Another option is using a closed in-line cable mount jack (like a Switchcraft 121) rather than an open jack & enclosure.  It would not need an enclosure and can be strapped to the inside of the cab.

https://www.newark.com/switchcraft-conxall/121/connector-phone-audio-jack-2-position/dp/39F247

2
Amplifier Discussion / Re: 80's Era Roland JC50 blows internal fuses
« on: November 07, 2021, 01:50:51 PM »
With that serial number, the schematic on pg.7 of the file posted above is correct.

The following is assuming there is no issue with headphones or their adaptor which was mentioned above.
The jack wiring is very busy (7 pins in use instead of 5), and my guess is it may have been mis-wired from the factory.
The info on the layout vs schematic does not seem to agree with each other.
(layout shows connection #19 going 2 places, schematic shows 1)

If your Dad never used headphones he would have never known.
Wiring it up like the later version with a simpler jack would be a fairly simple solution.

3
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.

4
Amplifier Discussion / Re: Fender London Reverb
« on: September 13, 2021, 12:25:09 PM »
I've seen other products with schematics that mis-label +/-12V  as 15V.
That could be the case here as well.

If ch.2 always works well with no issues, I think your supply levels are ok.

Can we just call the fault for now as 'ch.1 cuts in and out' and take it from there?
Is that an accurate description of the symptom?

5
Amplifier Discussion / Re: Fender London Reverb
« on: September 09, 2021, 01:32:30 PM »
Is the transformer marked 019252 ?
Is it getting 120V at the primary, with both primary windings connected in parallel, as shown on schematic?
For 12-0-12VAC winding, your voltages measured sound right (+/-15V).
So perhaps the 12-0-12 is not what should be there.

Are you using a footswitch?  Common faults on this series of amps were the push switches (pots) and bad solder on every pin of the board connectors.

6
The Newcomer's Forum / Re: Just joined...
« on: August 06, 2021, 12:29:37 PM »
Welcome aboard eh?
Nice that Enzo isn't going to run you through the gauntlet.  ;)

https://getyarn.io/yarn-clip/5deb2609-3a32-43d6-ae89-5c151e6eb93a

8
The older Roland 'service notes' didn't have that much in terms of disassembly, but they do have board layouts, waveforms, and some hardware.
They are organized by serial number, nothing really about the year.
You can probably find yours here:
http://www.tangible-technology.com/schematics/Roland/?MA

9
An imbalanced supply might not cause the 'no output', but a bad IC could cause no output and imbalance the supply.
What are the DC voltages at pin 1 and 7 of the IC ?
Are the 1K resistors (R23 and R24 from that corrected schematic) in the +/-16V rails measuring good?  Are there no zeners regulating the +/-16V rails?

10
Amplifier Discussion / Re: Fender Champion 40 as a modding platform
« on: April 28, 2021, 09:44:21 PM »
Typo was in Flester's post.   :)

11
Schematics and Layouts / Re: Roland JC-40 Schematic
« on: April 14, 2021, 12:06:30 PM »
Sure.  Thanks for bumping the limit.   :)

12
Schematics and Layouts / Re: Roland JC-40 Schematic
« on: April 12, 2021, 02:42:53 PM »
I don't have the schematic, but would also love to see one.  This is a neat amp!

Tried to upload, but it's about half a meg bigger than the 5Mb limit.  If you want to bump the limit, I will attach.   :)

edit: nevermind, zipped

13
Amplifier Discussion / Re: Fender Frontman 212R with distorted sound
« on: March 14, 2021, 04:30:50 PM »
When I listened to the mpg file my first thought was "that's a bad speaker".
But then I saw that you verified them as good.
Exact same thing here.
Quite relieved to see it was actually the speakers and our instincts are still good.   :)

14
Amplifier Discussion / Re: 1983 Fender Showman Channel Switching Issue
« on: March 07, 2021, 10:55:00 PM »
Double check whether that slight distortion is there when you go straight into the power amp.

15
Amplifier Discussion / Re: Fender M-80 Chorus Bias/Avalanche
« on: March 07, 2021, 10:53:42 PM »
If they came from China there is a good chance they are fakes.

You could try swapping the output transistors between the good and bad amp channels.

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