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Hitachi CSP 680 - ex crustytv  

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EmleyMoor
(@emleymoor)
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This is proving to be a "one step forward, two steps back" kind of set, at the moment. I set up to measure one of the TR41 voltages, but could not, once again, get a raster or sound. Only about 200mV present. Checked fuses, seemingly OK, apart from possibly the two not on the circuit diagram, but they are harder to reach..

The fact that both my printer (due to consumables shortage) and laptop (due to CMOS battery failure) are out of action means I don't have access to the service manual in the same room as the set, complicating investigations, but both of these problems should be resolved soon.

When I have found suitable tools I will be getting the tuner out to investigate why it's partially seized. This will be done either while I'm waiting to deal with the printer and laptop or once I've got a raster again.

If I sort the tuner I would like to find a tuning ring, as this one is partially broken. If not, I'll be looking for another tuner ideally the same type (HU-548), but at a push the one from a CRP-145 (HU-518), as long as it has the knob with it. I have seen a few other alternative arrangements, and could go with those if necessary, but the tuner is one of the interesting things about these sets.

"Yes, a bit of wet string may get you a good TV signal here on four channels, but you'll have to dry it out to get Channel 5!"

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Posted : 29/08/2020 3:26 pm
kswhite
(@kswhite)
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Is this the model you had in your car phil

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Posted : 05/09/2020 4:34 pm
EmleyMoor
(@emleymoor)
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@kswhite Yes, of course.

"Yes, a bit of wet string may get you a good TV signal here on four channels, but you'll have to dry it out to get Channel 5!"

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Posted : 07/09/2020 7:41 pm
EmleyMoor
(@emleymoor)
Trusted V-Ratter Registered

Tests today showed, once again, no HT with plug K out of the deflection board. I have the power audio PCB out, and it seems to differ from the circuit diagram - VA903 is absent, solder is smooth, like it was never there.

I am planning to test the output from the transformer next, just to make sure the fault isn't there, before I dig any deeper into this board. All diodes I have found seem to be OK, fuses and resistors intact and those that are readable in circuit are right. Assuming all is well transformer side, I will try to identify how the circuit differs from the diagram. I will also try to check the two fuses that are not on the diagram, if transformer output tests show a problem.

If all this is sound, the power PCB will be the next suspect.

 

"Yes, a bit of wet string may get you a good TV signal here on four channels, but you'll have to dry it out to get Channel 5!"

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Posted : 12/09/2020 12:20 pm
EmleyMoor
(@emleymoor)
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All transformer voltages, and the chassis-mounted transistor and resistor in that part of the circuit, check out. The main capacitor, a 470µF/200V can, is outside the range of my meter, and could possibly be the cause, and to source a replacement at some point might be good, but I consider it less likely than other possibilities.

"Yes, a bit of wet string may get you a good TV signal here on four channels, but you'll have to dry it out to get Channel 5!"

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Posted : 12/09/2020 1:03 pm
EmleyMoor
(@emleymoor)
Trusted V-Ratter Registered

Instead of the cathode of CR39 connecting to the cathode of VA903, it connects to the cathode of VA901, via a wire link inserted as VA902. This seems to actually be how the board is marked. The vacant position for VA903 is between F903 and R906. Needing further tests, TR42 and all capacitors in the power part of the board.

"Yes, a bit of wet string may get you a good TV signal here on four channels, but you'll have to dry it out to get Channel 5!"

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Posted : 12/09/2020 1:40 pm
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