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    Pioneer RT-1020L sound output problems

    Heads are clean, several times as there was a buildup. Will check tape path, but service manual points to either the P.B. circuit or oscillator circuit as well as some semi fixed resistors and capacitors prior to the circuit itself.
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    Pioneer RT-1020L sound output problems

    Thanks Rich P, I already gave all switches a good cleaning, but I did not yet do the bias pots on the circuit boards (found these on the bottom while exploring) Though my issue could be both the P.B. circuit amp and the oscillator circuit, I was hoping someone might have some experience with the...
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    Pioneer RT-1020L sound output problems

    Hi all, I recently purchased a Pioneer RT-1020L and after cleaning and lubricating, I gave it a test. Well, not surprising, the 1973 machine was not without problems. I checked the threads here as well as Google and also downloaded the service manual. My question is this; when recording, there...
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    Akai 4000ds MK II

    Got the 4000db head block, compared it to my 4000ds block, wire-wise, they are the same. I spliced the DS connector onto the DB block for the erase/record heads, soldered the playback wires to the PC board (no connector on DS model) and did a test. All seems to work well. Thanks for the help.
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    Akai 4000ds MK II

    Missed the question. The swap is between version 1 of the 4000ds or db ( 2 round plugs) and a 2nd gen MKii version rectangular white plug. Can I splice the MKii connector onto the blue, yellow and gray wires of the 1 gen heads. Wiring is same color on both as well as the playback head. Is there...
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    Akai 4000ds MK II

    Thanks for the advice, but the original question still stands, I'm a newbie to understanding schematics, so I asked if I can swap the MKii connection onto the first version of the 4000db/ds head assembly. I guess I'll see if I can see any difference in the signal path. Is there an Akai guru...
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    Akai 4000ds MK II

    Head block difference in MK II I purchased a 4000ds MKII in good condition other than the left input pot is flaky. It ether supplies no signal or pins the VU meter. I just cleaned it (deoxit faderlube) as well as all the switches including the famous SW9 record/playback one. The other issue is...
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    Just got the Realistic LAB-500 Special Edition (Pictures)

    Sorry to raise this old post, but I'm about to pick up a LAB 8500 and wondered if anyone found a user's manual or service manual for this unit? The seller says it has a hum, but I think the table/cartridge was not grounded. It should look awsome with my YAMAHA CA-1010. Thanks.
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    Yamaha C-6 Intermittant Power on Relay issue

    OK, will check these out next time I take things apart, as mentioned above, not the quickest to repair things. As for the Service Manual, I downloaded a scanned version of the service manual but the scan seems to be a fax scan and the circuit board/ part location diagram images are dark and...
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    Yamaha C-6 Intermittant Power on Relay issue

    LOL... Yea... I'd rather be listening than repairing... plus, as you can see by the pictures in the first post... disconnecting and reconnecting in the tight area is such a pain... As for the power switch, Yup, it got sprayed.
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    Yamaha C-6 Intermittant Power on Relay issue

    Finally got around to swapping out the C470 & 472 caps... problem still exists. Seems the longer the unit is off, the more chances it doesn't "click in" upon start up. Can someone send me a pic and part list of the other issues with these pre-amps (i.e. relay driver transistors, cracked solder...
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    Yamaha M-4 power up issue

    The M-4 is alive again... LESSON: Never troubleshoot and repair your amp late at night or when you are tired. I had found the initial problem which was TR603 before I posted this thread. It tested open so I replaced it... BACKWARDS (dumbass)... When things still didn't work, I continued to...
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    Yamaha M-4 power up issue

    before calling it quits, I did the finger test and none of the "C" group were even warm. To test the for poor solder, I used the protruding pin on one side and a pin on a further away component to test for continuity, all passed. I also tried to measure their values... a few in the group did not...
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    Yamaha M-4 power up issue

    Tested all the leads and all passed.
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    Yamaha M-4 power up issue

    Thanks for all the help, but I got to call it a night! Will test the zener asap.
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    Yamaha M-4 power up issue

    With TR605 in the circuit, and I reverse polorize between emmiter and collector, I get very very very low resistance. In the regular test of that transistor, it tests ok.
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    Yamaha M-4 power up issue

    TR605 reads -5.7V on base and emmiter while the collector reads 6.4v... hmmm open transistor?
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    Yamaha M-4 power up issue

    look fine, no bulge, leaks or signs of failure, but I have not tried the "finger gets hot" test when placed on them.
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    Yamaha M-4 power up issue

    Step #1 shows 65V at E and +65/-65 even though B+ shows 60V
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    Yamaha M-4 power up issue

    TR603 emmiter is just under 12v, 11.56v to be exact.
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    Yamaha M-4 power up issue

    F603 measures 2.5ohms. The fuse rating is 500mA. Sorry, F602 measures 2.5ohms and not 2.5A and is also good and the rating is 500mA.... Funny that only F601 shows as 1ohm. How do you want me to measure the 1A and .5A?
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    Yamaha M-4 power up issue

    DC Offset is fine within range F601 is 1A while F602 is 2.2A, a lot higher than .5A like suggested. I'll remove the fuse and recheck it. B+/B- measure 60V +/- 3V 80+/80- measure 83V.
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    Yamaha M-4

    I somehow missed this post in my misery state... I checked and reajusted all settings, no change, relays are still not being triggered. Dumb question, do I need speakers connected to trigger the relays? I am thinking NOT as I remember hearing the "thunk" a few seconds after power on without any...
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    Yamaha M-4 power up issue

    Can anyone help with this? http://www.audiokarma.org/forums/showthread.php?t=467482
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    Yamaha M-4 power up issue

    One day I was listening to my M-4 for a bit and turned it off. I came back about 2 hours later and turned things back on only to find that the M-4 did not trigger the speaker relays nor did the speaker selector lights come on anymore. So, the power switch lights, but that's that, no speaker...
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