Search results

@RebelKat If you're comfortable with soldering and desoldering then it's absolutely a DIY job; this table is very easy to disassemble and reassemble. The circuit boards are easy to get at and well organized. As long as you don't damage the motor windings there isn't much that can go wrong. I...

@Gustav80swe In my opinion replacing the electrolytic capacitors is a sensible first step for any electronics more than 30 years old - this TT is nearer to 40. Even if it doesn't solve your specific problem it will deduct from the list of possible causes and you won't have to worry about Ecaps...

@Pinkmagnolia Not much to report so far, life has been far too busy. My current hypothesis is that the neon bulb is worn out and flickering creating the illusion of an unstable strobe, but I have not yet replaced the bulb to confirm this. How is your QL-7 doing? Any similar problems? Any...

@tcdriver Yes, I've done several other garrard turntables in this way, all with great results. I still use a 'Type A' for convenient stacking of 78s and 45s when I don't want to have to leave my chair. It has its' functional limitations, but in my opinion it's aesthetic charms more than...

@gadget73 I have a digital oscilloscope which uses a computer as its' screen. I have fairly limited experience with it, so would need some instructions on how to properly use it to trace the signal. It has a built-in single-frequency tone generator (5khz I think?). I also have a frequency...

@gadget73 R29 reads 0.7M, same as the other channel (R57). R30 reads 0.7M too, also same as other channel (R58). R29/57 should be 1.8M according to the schematic R30/58 should be 1.0M according to the schematic

@gadget73 Sorry if I was unclear. The balance pot reads as it should. Measuring from each 6AW8A pin 7 to ground shows around 400k on one extreme of pot rotation, and around 25 ohms on the other - for each tube. The readings are on opposite sides for the two tubes. I'll check R29 and...

@gadget73 The balance control seems to be okay. Around 400k in the middle position for both channels (pin 7 to ground on the 6AW8As). Value changes when I move the knob. At one extreme it reads 370k, at the other extreme (and the other tube) 425k. At the opposite extremes 20 ohms and 33...

My apologies for taking so long to get back here, had a busy couple weeks but am back on track now. Finally tonight got around to opening up the amp to do the recommended tests. I re-measured all voltages in the output section, and all match between channels with one exception: Pin 9 of the...

The Right Channel isn't working. It must be 'Channel 2' since that is the side with the 'mono phono input' on it. I have a .pdf also, but the file size was too large to upload. Content is identical.

Seems they turned out quite blurry after converting to JPEG and downsizing... What is the best way to post larger schematics here?

Somewhere I have the original owner's manual, couldn't locate it but I found a photocopy of the very same schematic. I also have a copy of the PhotoFact. Quite a struggle to get these small enough to upload while still large enough to read! Please let me know if these are clear enough, or...

I haven't plugged different speakers into this amp, but I plugged the same speakers into my backup amp (another GE 7700 actually) and they're working fine. I tested all voltages in the output section and everything seems normal, but I'll double check this evening when I have the amp opened up...

@jon_s I'm now uncertain that there ever was a problem with those 0.1uF caps... Somehow I was convinced that both of them were testing bad, so I replaced them, then thought one was testing bad... The next day both tested good, though it took the meter a few seconds to register. Maybe I was...

Photos showing the current state of the amp. I added a DPDT switch to adjust the loading for phono cartridges (47k to 100k) Also the wires you see floating in the 2nd photo connect the 'tape head' input to the power amp at the wipers of the balance control. Otherwise aside from replacing the...

@gadget73 Thank you for responding! Yes the other lead was on ground. PIn 7 is tied directly to ground as per schematic. I'm measuring ~425V (too high?) on pin 9 of all four output tubes. I do have a cheap oscilloscope that connects to a computer - it's the OWON VDS1022I... I'm still...

@jon_s , @gadget73 and/or anyone still paying attention to this ancient thread. I'm wondering if you could advise me on a situation since you seem to know your way around this GE 7700 (the 6973 version) amp... I followed the advice regarding replacing the selenium rectifier with a bridge...

Just wanted to drop some useful information here for future QL-7 owners: The arm lifter mechanism as shown in the QL-A7 (automatic version) service manual is different, and easy to service. The QL-7 manual makes no mention of how to change the silicon oil, and it took me quite a while to...

Does anyone have a guess as to what kind of silicon oil the QL-7's tonearm lowering mechanism uses? The service manual mentions changing the oil, but doesn't specify the viscosity. I know that 100,000 cst - 500,000 cst is the likely range, but is there a formula for narrowing that down? I...

Okay, that's the next thing I'll do. I believe EngineerNate gave me instructions for that in a previous post. Just to clarify though: My strobe IS lying to me?? And whatever the other problems are (strobe, motor, etc) they definitely are NOT slowing down the turntable once per revolution...

Notice post #20 on page 1 of this thread, I posted a video of the strobe. The flickering is best seen as a reflection above the strobe marking, and the wobbling is pronounced (though slightly less after EngineerNate helped me realize that I had my scope in dual-triggering mode when I went to...

Perhaps a clue? This wikipedia page: https://en.wikipedia.org/wiki/Electric_light#Discharge_lamp says (regarding discharge lamps in general) "More advanced electronic ballasts may be designed to maintain constant light output over the life of the lamp, may drive the lamp with a square wave to...

@JP That's great news, thanks for doing those plots! But does it mean that my turntable is definitely NOT slowing down once per revolution? Is the strobe actually giving a false reading? The neon bulb is aging and visibly flickering.. Could that be the whole problem? If so, how would I...

I'm know I'm getting a bit ahead of myself here, but I filled the bottom of the plinth with plasticine today. Even if I have to buy another QL-7 I'll probably use this plinth and arm, so not as crazy as it might sound. For reference, in case anyone else wants to do the same to their QL-7 in...

I replaced every electrolytic cap in the turntable, didn't replace the ceramic or film caps.