I'm assuming the following is a Japanese distributed schematic copy of the Teisco Checkmate 25. I've never seen the resistor power ratings noted like this on a schematic before. In the power rail I see 5kΩ 6P and 1kΩ 6P. Anode resistors like 100kΩ 1/2L or the resistors around the rectifier as 5Ω 1L.
1/2L = 1/2 watt?
1L = 1 watt?
6P = 6watt?
Japanese Resistor Values on Schematic
Moderators: pompeiisneaks, Colossal
Japanese Resistor Values on Schematic
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Greg
Re: Japanese Resistor Values on Schematic
Pretend it's a Fender amp (and it very nearly is). Fender doesn't bother giving power-ratings on their 1950s and 1960s schematics.
Assume every resistor is 1/2 watt, unless it's in the power supply. From there, guess that you would use 2 watt or 3 watt for those, just as you would with a Fender amp.
Note that the "trem roach" is drawn as 2 pieces ("Ne" for the neon bulb, "CdS" for the cadmium-sulfide LDR). A Fender trem roach probably has different characteristics, but should still work in a pinch. Be ready to have to move wires connected to the Neon bulb portion to deal with any noise that arises.
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Re: Japanese Resistor Values on Schematic
You would not want to use a 1/4 watt resistor anywhere in a tube amp just for noise considerations in the audio stream and especially for preamp plate load resistors.
I use 3 watt metal film for plate load resistors and there only one half again as big as a 1/2 watt resistor is .
I use 3 watt metal film for plate load resistors and there only one half again as big as a 1/2 watt resistor is .
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Japanese Resistor Values on Schematic
Thanks to all the replies. I have no intention of building this circuit. I searched and found the Teisco Checkmate 25 schematic after a friend purchased one of these amps from a Reverb ad, and asked me if I could go over it. Very PTP, and a bit of a rat’s nest inside. According to the Reverb ad’s description, the seller stated that the amp was “restored” with some slight modifications.
FWIW, here’s the Reverb ad link that shows an itemized list of the work the seller performed on the amp:
https://reverb.com/item/80731820-teisco ... y-restored
To add to the entertainment, I’ll later post the few pics I took of the insides. Be warned!
FWIW, here’s the Reverb ad link that shows an itemized list of the work the seller performed on the amp:
https://reverb.com/item/80731820-teisco ... y-restored
To add to the entertainment, I’ll later post the few pics I took of the insides. Be warned!
Greg
Re: Japanese Resistor Values on Schematic
Forgot to take a pic of the front. The amp came without the rear panel.
After this pic, I ended up replacing the two set of dual caps, and cleaning up the wiring in this area.
The reverb tank's four suspension grommets were in bad shape. Metal on metal contact.
These puppies are running at 445v at the plates. One of the reverb tank grommets is living a life of Hell.
Amp owner asked me if I could disconnect the tremolo effect from the circuit. How about an open plug into the tremolo footswitch jack...
These vinyl pads elevate the tank about an 1/8" enough to lessen the stress of what's left of those grommets. Not sure if the one closest to the power tube will survive long.
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Greg
Re: Japanese Resistor Values on Schematic
The first dual F&T 50u cap replaces the old dual 40u. The second dual 16u replaces the old 20u, which are about 10 to 15 years old and test at very low ESR values, and don't have diarrhea all over them.
The reverb is not very versatile, but the amp sounds good and definitely can contribute to some inspiring tones. The cleans have decent amount of headroom at the amp's rated 25 watts. Tremolo is awesome.
This is truly a beast of a resistor for a 25 watter:
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Greg
Re: Japanese Resistor Values on Schematic
To be fair, much nicer than the work from most "professionals" around here. At least they used mostly brand name parts and knew to get rid of the oil caps. Should be way more reliable with the f&ts. Nicely done. Price tag on that reverb listing seems very high to me.
Re: Japanese Resistor Values on Schematic
Agree! I even asked the amp’s owner on how much did he really spent on it, to which he replied with a “$200 less than the asking price”… Not great, but not bad either. Amp seems to be purring along, and the power tubes tested very strong on my Maximatcher power tube tester. The Teisco head cabinet is very low profile, and therefore I also suggested to the owner to consider enhanced ventilation for the amp. Those power tubes are creating a lot of heat within its small housing.
Greg