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Yes, one of the zener diodes has failed - D362. Of course, that might have gone when I shorted the associated transistor. The other diode (D363) is fine.

Thanks for the tip regarding the probes...I'll do that when the new transistors arrive. Did you mean "test the capacitors and the zener diode connected to the base"? I can see the diodes and there are caps connected to the base, but no other transistors in that part of the circuit that I can see.

Great...so I was trying to measure voltage at a transistor on the power supply board (Q351 one of a pair associated with voltage regulator) that are attached to a heat sink), and my probe slipped and shorted out the transistor - flash and a puff of smoke, and now of course no sound at all...

Thanks Dr. Audio - I will do that! I also note this only occurs when the units warms up - from a cold start it plays perfectly at any output level. That would also suggest movement with heat expansion, so a bad solder joint might well be the issue! :)

Jon, it does not occur at all when using headphones only. When listening to both speakers and headphones, it occurs and can be heard both via headphones and speakers. So it appears related to something affecting the FM signal itself. I say this because AM is unaffected regardless of listening...

I have a problem with an LXI (Sanyo) 562 receiver (75w per channel) that only affects FM. 1) It works flawlessly on AM, Phono, AUX at any listening level up to full volume. 2) On FM and FM MPX it only works well up to about a 1/4 turn of the control. Beyond this level, loud distortion...

I will try all of those and report the results - many thanks!

When playing a tape, mainly it plays perfectly, but intermittently the assist motor kicks in a few times and there is a transient gap in the music. It seems to get worse toward the end of the tape, which makes me wonder if it's not a back tension issue? I have the service manual on pdf, and it...

Just bought a nice PS-X6 off Craigslist. The seller told me he could get no sound from it. After a little disassembly of the unit I find that the tonearm wires have been severed (pulled) from the base of the arm - so a rewire is necessary. The TT works well other than that, and is great...

Thanks. I read EW's post and also watched a video of how to do this. I will record the readings and post the results here in a few days (in the middle of selling our home, so am under orders not to be constantly working on gear in our kitchen)!

Do I just remove and test the transistors on the top board (the one with the missing fuses)?

Voltage selector was set at 100V Have tested all 8 out of circuit and readings range from 0.04 to 0.09

How do I test the transistors in this case?

Such as a bad resistor?

When Livin4 said that the top fuse readings F03 and F04 were bad, is that taking into account the fact that I was only taking a reading at one side of the fuse connector (because those two fuses have been removed, side the downstream reading is zero, as no AC power is getting there, of course)...

OK...using a Fluke 8060A digital meter (0.07 base resistance reading) I measured the resistance of all fuses with the power off, and these are: Top board: F01 = 0.07 Ohms F02 = 0.21 Ohms Bottom boards: All fuses read 0.10 Ohms

I have a QRX-7500, but someone has removed the top fuses F05 and F04. I get no click from the relay. I have followed testing suggestions posted elsewhere by Livin4 regarding the 2 remaining fuses (01, 07) - and get 7.52v and 7.43v AC for fuse 01 (lights) and 28.63v on both ends of fuse 07. The...

I have the same receiver, but someone has removed the top fuses F05 and F04. I get no click from the relay. I have followed your testing suggestions regarding the 2 remaining fuses (01, 07) - and get 7.52v and 7.43v AC for fuse 01 (lights) and 28.63v on both ends of fuse 07. The unit lights up...

Thanks. I have those, as well as the service manuals and schematic, all from that same website. The service manual describes the head muting circuit on p.19 http://www.hifiengine.com/library/pioneer/rt-909.shtml but I'm not really any wiser about how to check for a fault. Perhaps someone...

I have other 4-track machines, and tapes that play normally on those play with this issue only on the RT-909, and then only when playing forward - they play perfectly in reverse mode, so it can't be the tapes. I don't have manual yet, but I will get one and try to see how the...

Today I bought a mint-looking RT-909 from a yard sale; it works beautifully in reverse, but in forward play I can hear all four tracks (that is, both the forward track and the reverse track, which is of course playing backward!). Does the RT 909 deck have any kind of head mute switch that...

Ha ha...yes, but a lot on my plate lately, so not signed in as much as I'd wish...thanks for the information/advice. I have just received some 0.68uF film caps and will try these. Here was what I ordered from DigiKey: P4615-ND 2.41000 2.41 T CAP FILM 0.68UF 250VAC RADIAL COUNTRY/ORIGIN: CHINA...

Would this work, then? http://www.mouser.com/ProductDetail/Xicon/146-MET2E684K/?qs=sGAEpiMZZMv1cc3ydrPrF82zOBAub%252bPc0U0j2iKYRrA%3d Manufacturer: Xicon Product Category: Film Capacitors RoHS: RoHS Compliant Details Product Type: General Purpose Dielectric: Polyester...

It has the following marks: MPCON-M CEMC-2A704 0.7uF 250W VA.C CHUETSU What type of cap is that likely to be? Do you reckon Mouser might carry one that would work as a replacement?

Just bought a Sony PS-5520 non-working deck. There isn't a belt fitted yet. The drive motor should turn when set to manual play, but other than a quarter spin, the motor turns no further. Turning the pulley by hand it is obviously not seized in the motor bearings. I noticed how warm the motor...