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Messages - g1

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1
Preamps and Effects / Re: Award Session/Morley JD10 pots
« on: January 12, 2022, 12:13:41 PM »
RE: JD10 Pots:
I know this thread is old, but all this drama and not one person actually answered the original question?
Check the last post right before yours, he mentions the originals were log pots.   :)

2
Amplifier Discussion / Re: Heathkit TA-16 Tripping Breaker
« on: January 04, 2022, 08:32:15 PM »
Is it the same breaker tripping every time?
Does your meter have a peak hold function or anything like that?  It may be that the meter is just too slow.
If it's not too involved, you could swap the breakers around and see if the problem follows one particular breaker.  It's not common, but they do get weak sometimes.

3
Schematics and Layouts / Re: Randall Century 100 schematics?
« on: January 02, 2022, 10:36:26 AM »
So you have found out that a continuity 'beep' is not the same as a short.  That is a good thing to know, as it leads to many errors for novice users.  Different brands have different ranges that will cause the beep, some anything below 40 ohms, some as high as 200 ohms!
If you know the spec for your meter, continuity function can be useful.  But usually for things like looking for an automotive wire that is shorting to the chassis or something.
When reporting resistance always use resistance range.

The 7 ohms you measure at the headphone jack will be the speaker in parallel.  And the common way to disconnect the speaker for headphone use is to disconnect the ground side of the speaker via a switch contact in the phones jack. (with attention to what Phil said about current feedback resistor)
If you have an empty TRS plug to put in the phones jack, it might help with the resistance readings and wiring tracing.

4
Amplifier Discussion / Re: newbie question about cranked amp overdrive
« on: December 28, 2021, 02:52:44 PM »
Any source for the schematic?
I could be wrong, but it seems we have not even found out the model # yet?
Perhaps that would be a little bit helpful?  ;)
Mentioned on the first post, Also I linked to a few pictures I found on Reverb site in (post 15) ;)
Phil.
I'm not trying to be difficult, but unless I am blind, there is no model # in either of those posts.
Schematics are found by model number.  If we had the number, perhaps we would already be looking at the schematic, which would make for a much more fertile discussion.
Apologies if there is no model # to be found on the unit, but if so the OP should just say that.

5
Amplifier Discussion / Re: newbie question about cranked amp overdrive
« on: December 27, 2021, 02:28:37 PM »
Any source for the schematic?
I could be wrong, but it seems we have not even found out the model # yet?
Perhaps that would be a little bit helpful?  ;)

6
It's a DB604. According to the datasheet that's a 400V, 3A.
I saw that data sheet, but in general I expect a 604 bridge to be rated at 6A 400v. 

Was that a download, or was it the 'specs' listed on the datasheets360 page?
That 'specs' page looks to be their own list with a typo.  The pdf they offer on that page shows the part to be 6A. (see attached)

7
With 4 ohm load, 100W requires 5 amps.  I think you need some leeway there.  I would guess 8 to 10A would be much more reliable.

8
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

9
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.

10
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.

11
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?

12
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.

13
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

15
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

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