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Glad to see you got yours working! I still need to track down triggering/sweep-start issues but am currently stumped as to why one segment of sweep timing isn't working (50ms, 20ms, and 10ms).

FYI, I found that the transistor Q728 - at the output of the "main sweep start comparator" - Base-Collector junction was open circuit while Base-Emitter was OK. Strange, unexplained failure mode for

I bet you're right, Paul.... Didn't think about the pulse having to be sufficient to get across the LED junction. So far I have only done repairs on incandescent strings. So the old axiom raises

I have built a couple of these for 465/475. If memory serves me correctly you will need 6 - 20kV diodes and 6 - 1000pF 20kV ceramic caps and a 470k 1/2W resistor. I bought the caps and diodes from

Hi Jim, I'll have to disassemble the cams once more; however, I don't recall seeing an elongated hole in either end of that drum. The hollow shaft isn't constrained for axial excursion much at all

I've operated 70's 80's Radaranges too! The power is low now as the magnetron tubes aged. I'm thinking of adding new DC driven 250 Watt oscillator modules and taking the old transformer and

Really? I've never heard this before. So they are expected to "ring" to give higher voltage than would otherwise be expected? That seems like it would be hard to control, even with a +/- 3%

Dead cells would leave their two terminals effectively shorted, while removed cells leave the terminals open. I have no idea if that would make a difference here.

This sounds like the same problem that I've fixed on a number of 465 sweep drum switches. The rear drum rides on a plastic drive dog that was overmolded onto the 1/8" hollow shaft. With time and

In AUTO mode, any sweep ramp is followed by some HOLDOFF time, during which the sweep circuit watches to see if it gets a triggerable signal from the input. If a triggerable signal arrives during the

I don’t like “shotgun” repairs, but have you tested the HV diode yet? In the old microwave ovens with the heavy iron transformer, this was the usual failure mode. But usually the diode

This is explained in this service information... just one picked at random, as I got interested although my microwave

Hello, I did pretty much the same thing to check the horizontal amp. I removed the horizontal preamp and I injected two triangular signals in opposition of phase in the pins 2 and 7. The spot moves

Hi I have a similar situation. The Transformer is OK -Checks out. But am now thinking it might be the EHT pump rectifier. However do you know where I can find out how to build the HV Tripler. Just in

I have a T935A that is blowing HV fuse. It's rated at 62mA but the R458 is drawing 120mA. (I measure it via DMM instead of the fuse, but only turn on the scope for a few seconds.) This is after I

Thanks for the offers and info, I'm not sure if I specifically need the -03 version.. I don't suppose Tek ever released datasheets or info on these parts? I'll reply to those who messaged me and work

Hello Jim, There is one other possibility that has not been mentioned in this OT discussion thus far and that is the very basic protection mechanism implemented by a combination of limit switches in

The cap is discharged. If the trip point at pin 6 is 5V it will take 0.4 time constants. That would make ~ 20Hz rate if it could fire back to back. Datasheet says trip point is 4.2V +/- 0.3V and the

I have minor knowledge of Microwave ovens, but you have a large current draw when it fails, to dim your kitchen lights and blow a 20amp ceramic fuse (those tend to be slow blow), and you did nothing

Hi Ozan, I was tempted to ask for that but thought it wasn't available. That should answer several questions! Thanks, Barry - N4BUQ