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March 30, 2020, 09:15:20 PM

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1
Amplifier Discussion / Ampeg Vh140c power transformer replacement
« Last post by Ratsapprentice on Today at 06:55:17 PM »
Hi guys,

I’ve had a Vh140c running through an external step down transformer for years (I’m in the UK, and the amp is a US model)and would really like to be rid of it. But I’m having a very hard time finding a suitable 230v PT.

Any help would be massively appreciated.
2
Schematics and Layouts / Re: 5th Gear Overdrive v3.0
« Last post by joecool85 on Today at 08:20:02 AM »
Thanks for posting that. Looks cool, might try it.

Which diode is the LED and which is the 4148?

Can two general purpose NPN transistors be configured as the darlington, or does the sound depend on the characteristics of that particular transistor?

Phil in gorgeous Young Harris, Georgia, USA

It doesn't matter which diode is which as long as you have them facing opposing directions.  I haven't built it with general NPNs as a darlington, but others have on diystompboxes, and it seems that it works fine.  That said, I had another person build it and try a bunch of trannies and couldn't get the exact same sound as MPSA13 with anything else - close enough to work, but not quite the same.  Take that for what it's worth!
3
Schematics and Layouts / Re: 5th Gear Overdrive v3.0
« Last post by paelgin on March 29, 2020, 09:38:42 PM »
Thanks for posting that. Looks cool, might try it.

Which diode is the LED and which is the 4148?

Can two general purpose NPN transistors be configured as the darlington, or does the sound depend on the characteristics of that particular transistor?

Phil in gorgeous Young Harris, Georgia, USA
4
Amplifier Discussion / Re: Customized Kustom 12 Gauge
« Last post by Unique Amps on March 29, 2020, 08:12:43 PM »
Thanks for the welcome and speaker vote!  Duly noted.

 :tu:
5
Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« Last post by galaxiex on March 29, 2020, 05:40:02 PM »
Got the coil wound and installed.  :)

4760 turns and 662 ohms.

It's alive!
We have reverb!
(albeit not very good reverb, but I expected that  ::))

Now I'll disassemble the tank and clean it up some,
just to get rid of some of the corrosion.

Edit: This is the output coil that I just wound at 662 ohms.
No idea what it was originally, or what it's supposed to be.
Seems to be working fine.

The input coil measures 1K6 ohms DCR and both coils were/are wrapped with blue tape.
I don't know if the tape color indicates coil impedance/DC resistance like the Accutronics tanks.
6
Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« Last post by galaxiex on March 29, 2020, 03:27:00 PM »
Ok, the reverb coil winding has started....  :)

First pic is the bobbin mounted to the winder with the old wire still on it.

Second pic is the new wind started.

Wow this thing is tiny!

Winding going really sloooow cuz I don't want to break the wire and hafta start over...

The new wire is thicker than the old, so I'll over-wind it somewhat.

Old wire measures .015"
New is .025"

I was able to find the end wrap and paid attention to the direction of wind.

New wind is going on the same direction, don't know if it would matter (phase issue, maybe?).


7
Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« Last post by galaxiex on March 29, 2020, 12:16:14 PM »
Here's some modifications to the little CM-22.  :)

Pics show the added stuff.

The input buffer is just hung on some stiff wires, right on the input jack.

The added C24 and R39 (see schematic) give a large gain boost,
very "crunchy" germanium transistor distortion, almost Fuzz Face territory.  8)

I tried with just the 100uF cap and it was too much gain, squealing feedback.
The 1K resistor tames it just right.
Thinking to maybe put the C24, R39 "gain boost" on a switch...

Last pic is a size comparison of the power Tx.
The bridge rectifier setup is temporary, I'll make a little board for it.

Can you tell I'm bored with being stuck at home?  ;)

Edit; still haven't fixed the reverb tank, I'll get to that later today... maybe...


8
Software / Re: Zoom G5 software
« Last post by flester on March 29, 2020, 08:50:17 AM »
Or any other way to get acoustic instruments talking to a computer.

Sent from my SM-A505FN using Tapatalk

9
Software / Re: Zoom G5 software
« Last post by flester on March 29, 2020, 08:47:03 AM »
I have my Zoom working now as an interface to the PC. I am using Jamkazam for  online jam sessions. Works fine for electric and electro-acoustic but can't get a good  sound with a dynamic mic. Any suggestions on that?

Sent from my SM-A505FN using Tapatalk

10
Schematics and Layouts / Re: Peavey Mixer: PV8USB Schematic and Repair
« Last post by paelgin on March 28, 2020, 05:51:56 PM »
Here is a picture from the repair in process.  I have removed the seven known-bad preamps using ChipQuik.  Here is a picture after removing one of the chips and cleaning with solder wick to remove the excess solder.  The chip is a 4565 in SMD form (square, 5mm per side) apparently (hopefully!) and I've got 10 on order (at less than the unit cost of $0.39 each at Mouser).

I will try to keep this thread updated as I progress.  The PV6USB models that I repaired were only broken in the power supply, so this is way out there for me.

Phil in gorgeous Young Harris, Georgia, USA
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