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Hello to all.
I'm restoring my late '60s TEISCO Express 7 (aka Check Mate 18) and need help on the reverb circuit. The tank consists of 2 small single units wired in parallel, as Enzo described in a previous post (http://music-electronics-forum.com/s...ead.php?t=1841).
One of them was broken and found an Accutronics unit to use as a possible replacement. The model number is 1FB2C1B; this has a high input impedence (1475 ohms), as this amp uses a capacitor-driven reverb.
The tank seems to be OK (input & output resistance 160 ohms) but when connected there is no reverb even with control pot at max. Disconnecting the cable from the tank output and touching the tip of the plug with the reverb control turned up, there is a loud buzz from the speaker, showing that the return circuit is OK.
I would appreciate your suggestions in making this work.
PS. A schematic is here: http://www.schematicheaven.com/barga...eckmate_18.pdf
There was a resistor (100k) from the tank output to circuit ground that's not shown in the schematic. I don't know if it should be used as it is not present in any of the other models (CM-20, CM-50) as well.
I'm restoring my late '60s TEISCO Express 7 (aka Check Mate 18) and need help on the reverb circuit. The tank consists of 2 small single units wired in parallel, as Enzo described in a previous post (http://music-electronics-forum.com/s...ead.php?t=1841).
One of them was broken and found an Accutronics unit to use as a possible replacement. The model number is 1FB2C1B; this has a high input impedence (1475 ohms), as this amp uses a capacitor-driven reverb.
The tank seems to be OK (input & output resistance 160 ohms) but when connected there is no reverb even with control pot at max. Disconnecting the cable from the tank output and touching the tip of the plug with the reverb control turned up, there is a loud buzz from the speaker, showing that the return circuit is OK.
I would appreciate your suggestions in making this work.
PS. A schematic is here: http://www.schematicheaven.com/barga...eckmate_18.pdf
There was a resistor (100k) from the tank output to circuit ground that's not shown in the schematic. I don't know if it should be used as it is not present in any of the other models (CM-20, CM-50) as well.
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