Teisco Checkmate 25

nick

Girlfriends dads old amp, absolutely mint. 15" Pioneer speaker, has Trem and Reverb. Not a highly collectable or desireable item but definately has that lovely old vintage valve sound. 8)

bottledtone

Serious cool! 8)
Sometimes it is better that things are not too collectable, and then you can get a sweet deal for a vintage tone.

Jack-Flash-Jr

Get famous and then everyone will want one! That's what Jack White did for those plexi guitars...
It looks like you can get a serious rumble out of there!

Cannon

Awesome amps!!! Me and my mate both had that same model amp. Sold mine but he still uses his.
I think its been giggin live with no fault for probably 15 years with his. And remember those amps were built around 69!

Nice!
8)

Karel-Mars

I have worked on some of these. They were usually hand wired point to point with lots of leaky oil caps; similar to the ELK amps. It probably came out of the same factory.

If my memory serves me it had an EL84 power amp/two channels with reverb and tremolo. Nice sounding amplifiers with a slow attack. I guess they would be good for gritty jamming.

If it has Matsushita tubes inside, keep them. They are very good tubes. I read somewhere that RCA sold their tooling to Japan and this was used to manufacture Matsushita tubes; thus Matshushita=RCA.

Karel-Mars

I have just worked on a Checkmate 25 and can post more details:

This amp does not use EL84's! It needs 7189's which are similar to EL84 but can take significantly higher voltages without self destructing.

7189 Ratings
Vh Ih VaMax Vg2 Max Pa Max Pg2 Max
6.3 0.76 400 300 12 2.0

7189 Application Data
Class Va Vg2 Vg1 Ia Ig2 Zout Pout
AB1 400 300 -15.0 15.0 1.6 8,000 24.0

You can get 24 watts out of 7189's - thus "Checkmate 25" This is only possible with fixed bias; which the Checkmate 25 has.

Compare that to EL84

EL84 Ratings
Vh Ih VaMax Vg2Max VhkMax PaMax Pg2Max IkMax
6.3 0.76 300 300 100 12 2 65

EL84 Application Data
Class Va Vg2 Ia Ig2 Rk Zout Pout THD
AB1 P/P 250 250 62-75 7-15 130 shared 8,000 11 8
AB1 P/P 300 300 72-92 8-22 130 shared 8,000 17 10

You can get 17 watts out of two EL84's in push-pull with MAX 300V between the anode and the cathode. Thus the "18 watter"

nick

Karel wrote: I have just worked on a Checkmate 25 and can post more details:

This amp does not use EL84's! It needs 7189's which are similar to EL84 but can take significantly higher voltages without self destructing.

7189 Ratings
Vh Ih VaMax Vg2 Max Pa Max Pg2 Max
6.3 0.76 400 300 12 2.0

7189 Application Data
Class Va Vg2 Vg1 Ia Ig2 Zout Pout
AB1 400 300 -15.0 15.0 1.6 8,000 24.0

You can get 24 watts out of 7189's - thus "Checkmate 25" This is only possible with fixed bias; which the Checkmate 25 has.

Compare that to EL84

EL84 Ratings
Vh Ih VaMax Vg2Max VhkMax PaMax Pg2Max IkMax
6.3 0.76 300 300 100 12 2 65

EL84 Application Data
Class Va Vg2 Ia Ig2 Rk Zout Pout THD
AB1 P/P 250 250 62-75 7-15 130 shared 8,000 11 8
AB1 P/P 300 300 72-92 8-22 130 shared 8,000 17 10

You can get 17 watts out of two EL84's in push-pull with MAX 300V between the anode and the cathode. Thus the "18 watter"

are these valves available? and are they more expensive than EL84s? Girlfriend says it makes odd noises so I assume it has leaky caps and the valves are original from the 60s so it may be time to replace.

Karel-Mars

Here's the link to 7189 at tube depot

http://www.tubedepot.com/so-el84m.html

Mr Valve should also have some in stock.

Gunfighter

Hey man, interested in selling at all ? I have just the head, but looking to buy both head and cab.

nick

Gunfighter wrote: Hey man, interested in selling at all ? I have just the head, but looking to buy both head and cab.

Amp has sentimental value, I highly doubt they would sell unfortunately.

Gunfighter

Cool, well I also live in Durbanville - so if they do ever wanna sell then please let me know. Thanks man..

Reinhard

That looks pretty damn cool! Coily cable FTW

Sidecar

I just picked up a Firstman Vanguard 250, it has 3x 12ax7's and 2x 7189 power tubes, all Matsushita. It looks completely original on the inside, and has never gone for a service since the previous owner bought it in the early 1970s. But it does need some servicing, hopefully nothing too serious. Sounds great though!