Hello,
As the title says, this is about a Binson echorec all transistor version. I´ve been trying to fix this for a friend who bought it in "original" condition. That meant replacing every wire and many bad components. Unfortunately, I´ve now reached the point where I can´t find a solution.
The trouble is that the outputs from the record heads are distorted-- it looks smeared if that makes any sense. There is a large kink in the middle of the signal and the waveform is stretched considerably. I believe I´ve narrowed the cause to the record amplifier or the actual record head.
Now, when I look at the signal on the record head itself I can see a very clean high frequency sine wave which I assume to be the bias. However, when I look at the junction of the 22k/470n on the driver transistor the top of the waveform is severely chopped.
-- I should mention there appears to be some confusion here in the schematic and the actual board in front of me. First off, the BC140s have been replaced with BC211s. Since this is across the whole unit, I would assume it is just a later or earlier iteration. In the unit in front of me, the collector resistor was originally 2k2, the emitter was not bypassed, yet the coupling cap was also 470n. I changed the 2k2 to a 22k which brought the voltage on the collector more in line with the schematic (with 2k2 it was around 22V.) However, the emitter still sits well below 3.5V at around 1V.
I am assuming that the attempt is to get as clean a signal as possible with a lot of current drive here. If this could be better achieved with a more modern circuit I´m all ears. My friend isn´t worried so much about the collectable value as having a nice sounding echo.
Of course this could all be moot if the record head is shot. I am just uncertain how to determine where the problem lies at the moment...
Thanks for all your help!
Topic: Binson PE603T echorec delay help (Read 5722 times)