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April 04, 2020, 11:48:09 PM

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1
Don't Worry - It's grounded!

Cheers for the help.
2
Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« Last post by galaxiex on Today at 02:00:32 PM »
Ok, some more mods.  :)

Added a buffer at the mix point of the volume and reverb.
The high pass filters at the output of the op-amps (C23, R38 and C26, R43) cut unnecessary low frequencies.
Corner frequency of the filters is approx 88 Hz.

The filters helped a lot to get rid of the amp sounding muddy/mushy/smeared sound.

Now... I think the mix point of the vol and reverb could use some help.

The way it is now the reverb sounds like a completely separate signal sort of "riding on top of" the main signal.
IOW it doesn't sound "mixed".
Hope that makes sense...

Any suggestions on how to "more properly" mix the 2 signals?

Thanks for any help!   :)
3
Schematics and Layouts / Re: Peavey Mixer: PV8USB Schematic and Repair
« Last post by paelgin on April 02, 2020, 11:18:47 PM »
I have replaced the one open zero ohm SMD chip (jumper), three bad SMD resistors and seven of the SMD ICs (parts removed and locations circled in attached picture). 

I found two more ICs bad (circled in black, in the headphone and control room outputs).  I also found three more out-of-spec SMD resistors (4.7ohm, reading over 8 ohms each).  Two of the three 4.7 ohm resistors are spec'd for 1% tolerance, so I will get them all like that.

I expect parts to be delivered tomorrow and will try to get it done and working.

Phil in gorgeous Young Harris, Georgia, USA
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Schematics and Layouts / Re: 5th Gear Overdrive v3.0
« Last post by paelgin on April 02, 2020, 10:55:50 PM »
Thanks for the clarification. 

But, but, but... I don't know if I can afford that because that one Darlington transistor costs 45 cents each!  (Mouser, as of 4/2/2020).  lol

Of course shipping is $7.99, so I wish I had seen this yesterday (I ordered the 2nd round of parts for the Peavey mixer I am repairing), but I forgot to turn "Notify" on.  I'll see if I need more stuff once I get the known bad parts replaced.

Phil in gorgeous Young Harris, Georgia, USA
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by phatt on April 02, 2020, 09:54:56 PM »

Take it to a teck shop, they will know where to source a new Tx. while you are there it looks like you have NO MAINS EARTH. ouch!!!
The tecks can install a new power cord with Chassis EARTH.
These things can be a Death trap without an earth.  :loco
Phil.
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by g1 on April 02, 2020, 09:51:04 PM »
Looks like there is only 4 wires coming out of the transformer, 2 red (secondary) and white & black (primary).
So it's not the export version of the transformer and can't be changed by wiring.
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by Ratsapprentice on April 02, 2020, 02:57:19 PM »


There you go.
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by Enzo on April 02, 2020, 12:30:01 AM »
I read it this way.  The schematic doesn't say export model transformer, it points out the export model WIRING.

It does appear to be a wiring change.
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by g1 on April 01, 2020, 09:26:06 PM »
Does the power transformer have 7 wires coming out of it?
4 of them should go to a board with a fuse on it (07-315-01).
Like Phatt said, take a close up picture of that board and post it.
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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« Last post by phatt on April 01, 2020, 09:24:09 PM »
Wire taps won't be inside the Tx.

With power cord removed from wall, Follow the incoming Mains wiring.
the sequence will be something like this;
Fuse> switch> THEN look for a tag board or block connector with mains wires that also go to the Tx.

If the Tx primary has dual winding's then there will be at least 4 mains wires between the block con and the Tx. (not to be confused with the secondary wires)
You may even find the numbers on the schematic are also printed on the tags.

Like I said; Take a picture of that section of the amp and post it, that will speed up the answer much faster than us trying to guess it all. hint.  8|
Phil.
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