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Messages - galaxiex

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Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« on: March 22, 2020, 01:11:23 PM »
Here's some mods so far....

3 wire power cord and a fuse!!!  :o
Also got rid of the "death cap", C20 in the original schematic.

C1 and C7 changed to 100nF, altho C7 is not doing much right now as the reverb tank is still out.

Removed the aux speaker jack and put the fuse holder in that hole.

More mods to come....

Input impedance is dismal, so a buffer on the input is in the plan.
Possibly a (slightly) bigger power Tx and full wave bridge rectifier.

Edit; schematic removed, mistakes were made, corrected schematic in post below...

Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« on: March 22, 2020, 01:02:05 PM »
Here's the badly corroded output coil.

I have already managed to get the coil bobbin removed from the core.

I have a pickup winder so I'll make an attempt to rewind the coil.

Schematics and Layouts / Re: Teisco CheckMate 22 schematic
« on: March 22, 2020, 12:58:50 PM »
Here's the corrected schematic...

Edit; added main voltage to schematic.

Edit 2; I made a mistake drawing the original schem, so here is the (again  ::)) corrected schematic.

Schematics and Layouts / Teisco CheckMate 22 schematic
« on: March 22, 2020, 12:56:07 PM »
Got this off the bay awhile back, just getting to it now.

Seller pics.

The seller said the reverb does not work and I found the tank output coil to be broken.
No surprise, considering the amount of corrosion in there...  ::)

The schematic inside the back panel is "not quite" correct.

I traced the board and drew a correct schematic. (next post) 


Amplifier Discussion / Re: My K-20X
« on: February 25, 2020, 11:51:53 AM »
Ohhh, DUH!

I didn't see we are on the second page!  ::)

Amplifier Discussion / Re: My K-20X
« on: February 25, 2020, 11:14:12 AM »
Here it is.

Please bear in mind that this looks different now as this was a test fitment.  The wires in this picture were connected to either end of R11 (one end lifted).  I have since removed R11 and now connect on the bottom side of the PCB to help with noise.  I have also added star grounding and replaced the metal speaker and line out jacks with insulated plastic types.

The schematic attached to the first post in this thread shows were I connected in.

Thanks for the gut shot, but I don't see the schematic attachment?

Amplifier Discussion / Re: My K-20X
« on: February 24, 2020, 06:46:10 PM »
That's pretty cool, Joe...  :cheesy:

Where in the amp circuit did you put the reverb?

I assume at the front end since it's a stompbox type circuit?

Gut shots would be great.  8)

Tubes and Hybrids / Re: Texas tone made simple
« on: October 24, 2019, 10:42:29 PM »

Excellent info and playing!  8) 8) 8)

Thanks very much for sharing!  <3) <3) <3)

 :dbtu: :dbtu: :dbtu:

Amplifier Discussion / Re: MaxTurbo mods
« on: June 19, 2019, 10:57:59 PM »
Nice work phatt!  8)

Never know when someone might need/want that info.

Thanks for documenting!

Amplifier Discussion / Re: Peavy Rage 158 no sound after 1-5 mins
« on: June 16, 2019, 11:47:17 AM »
Pin 3 of the TDA2040 is connected to the heat sink tab.

If the supply is single ended, pin 3 can be grounded, according to the data sheet.

If using a split supply, pin 3 and the heat sink tab MUST NOT be grounded.

Amplifier Discussion / Re: Another Randall RG100ES question
« on: May 22, 2019, 06:16:54 PM »
Looks like a CTS pot.

The number 137 is the EIA code for CTS.

The next 8929 is the date code. Probably 1989, 29th week.

The other numbers spec the pot.

Unsolder the pot and ohms measure from outside lug to outside lug to find the overall resistance.

Turn the shaft to center and measure ohms from middle lug to each outside lug.

Compare and if approx the same, it's a linear pot.

If one outside lug reads much higher (or lower) than the other, it's likely a log pot.

Got to DigiKey, Mouser, etc to find an equivalent.

DigiKey has the 450 Series of "Stock pots" that can be ordered/configured how you like.

Look in this pdf...

The Newcomer's Forum / Re: Heathkit TA16
« on: May 12, 2019, 12:12:57 PM »
You might benefit from having the complete construction manual for that amp.

It is available here>>>

for a reasonable price.

Heathkit manuals are very well done (step by step) and have a trouble shooting section to help diagnose problems.
You will learn a lot just reading the manual.

If you decide to get the manual, be sure to go to their home page and read the ordering info and about their manuals.


The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 19, 2019, 09:08:59 PM »

What an eejit. It so clearly has.

Just goes to show I need those readers or a magnifying glass. Age has not only caught up but overtaken me this last year... 

Thanks, again, Phil.

Yep I know the feeling, my eyes also struggle to see fine detail. :'(
I don't even bother to try and fix anything that uses SMD's.  xP
I agree with *galaxiex* about replacing Electro's in old gear but I would add this;
Only replace the obvious first and get the amp working,,, then go back and replace the others.
If you shotgun the whole lot and it still does not work then you have no idea if you added yet another mistake. :-X

Yep, very good point. Fix the obvious first.

The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 18, 2019, 06:38:09 PM »
I have worked on quite a few SS amps from the 60's and 70's.

I've found in all cases those amps benefit from replacing ALL of the electrolytic caps.

I used to test them (caps) and leave them if they "seemed good" but the amp(s) would still have problems.

If that amp were mine I'd start by replacing ALL of those blue tubular electro caps.

Just my $0.02

The Newcomer's Forum / Re: Amp repair?!
« on: January 28, 2019, 07:19:11 PM »
WOW galaxiex !!! Where on earth did you find this?! I love building little projects like that. Essentially I am making a step down transformer that is more portable than what I already have now and although I was looking for a more direct approach this workaround is certainly an option plus a bucking transformer is always a useful thingy to have on my bench. Thank you so much, where did this come from, do you have more projects you can share like that? I'd be very interested. Thank you!

You are very welcome.  :)

I got it from the Hoffman amp forum.
A member/moderator there by the name of "sluckey" is a pretty smart guy with amps.
That is his scrapbook of amp stuff.

Forum here.

Edit; Here's sluckey's web site...

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