#1915

Рет қаралды 2,525

IMSAI Guy

4 күн бұрын

Episode 1915
schematic doesn't match the manual.
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Пікірлер: 20

@henrybecker2842 2 күн бұрын

Really sorry you were sick for such a long time. It doesn't get easier for us as we get older. Hope you fully recover soon.

@jspencerg 2 күн бұрын

Hope you're feeling better.

@user-ch1gc3yy2y 2 күн бұрын

May the good health be with you! Glad you are on the right side of grass! And i Like your electronics videostories

@lmamakos 2 күн бұрын

Glad that you are on the road to recovery, even if not 100% yet. Please do take care and prioritize your health and well-being.

@nickcaruso 2 күн бұрын

Wishing you a speedy and complete recovery. Great series, particularly enjoyed this one.

@fredflickinger643 Сағат бұрын

Be well! Things are looking up on this instrument!

@allananderson5840 2 күн бұрын

Thanks for these videos! And hope your feeling better!

@deanbell5164 2 күн бұрын

I like your forceps, I have had mine for 50+ years now, and my father had some well before I was born :)

@SeanBZA 2 күн бұрын

Either levelling circuit has an open filter capacitor, so the signal is getting amplitude limited at low frequencies, or the levelling is oscillating because of an open tant, or has lost negative voltage rail to opamp.

@VV0RK Күн бұрын

Glad you are feeling better. I don't understand why there is an amplifier before the attenuator. I am just an arduino level hobbyist at this point so RF might as well be magic.

@Manf-ft6zk 2 күн бұрын

Very interesting to see all the details of the modules. I wonder about the holes in the shielded compartment shown in 3:32. It looks like a construction that was used for a different purpose before. I know such kind of holes from my constructions but I wonder why they are in a serious product. They will not harm the quality but someone made them and they seem not to be of any use here.

@arinascimento547 Күн бұрын

Hope you're better. The gold threaded rod belongs to the last RF power transistor in the chain. It's a transistor suited to stripline, I don't remember the package code now. It's the rod that was covered with the rubber.

@IMSAIGuy Күн бұрын

oh my gosh, you are right, didn't expect that.

@peterjones2411 2 күн бұрын

I don't think it's the leveling circuit I noticed the the gain falling as frequency fell the leveling circuit is trying to do it's job and increase gain of 3 stage amp and they are going into clipping instead of adding gain so I believe you were on the right track to start with but it might be a transistor behaving funny at lower frequencies. hope you're feeling better soon.

@jim9930 2 күн бұрын

Yeah, first rule of repair: Thou shalt measure supply voltages/currents. It is acting like an open (few tenths of a pf). RF voltmeter will show which stage - even a crude 470r on the end of a coax 'sniffer' into spectrum analyzer works. @ 10MHz a simple 10x scope probe with 470r on the end to keep capacitive loading small (Rigol FFT is safer than input of expensive SA for poking around) and you can still see DC voltages.

@bayareapianist 2 күн бұрын

Does it meaning the circuts before leveling circuit gets smashed when it gets loaded by leveling circuts?

@jim9930 2 күн бұрын

@@bayareapianist If the first stage of 3 stage amplifier had no power you would be driving into base emitter junction (diode short to ground) - every frequency would look clipped. If the last stage was open (no power or damaged transistor) - the previous 2 stages would be trying to overcome loss of gain and driven into clipping - most likely scenario - tiny picofarad feedthru. At 500MHz it is enough to allow the AGC levelling circuit to work (no clipping). At 10MHZ, not enough gain in the first two stages so you see clipping. Somebody probably accidentally shorted the output at +13dBm and 'cooked' the last amplifier transistor - no stepped attenuator between it and a reactive load (inductor spike ? ). Micro X package can't dissipate much heat, so it could simply have failed with age, too.