ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi. New member to this forum.
So, I got this unusual deck working and have been playing/recording for several weeks. A few days ago, the reel/capstan motor stopped working. The transport would rise when put into play, but quickly drop and shut down. Typical belt failure, right??/. NOPE...Belts OK. Examined a fuse associated with the motor operation -- IT LOOKED OK....So, I proceed to look for power supply problems, disconnecting the PCB near the transport with its 6!! flat strap-style/pin connectors carefully disengaged. All seems intact. (This deck is in really great physical condition.) After mucking around a bit, I finally remove the fuse (250mA, 250V) and check it with a meter. NO CONTINUITY!!! Great. Radio shack had 1, 4-pack of these fuses...amazing.
Put it in - reconnected all the darn strap connectors ---and--- the Motor is running. Hit PLAY...NOTHING. Hit REWIND....NOTHING. Now, the transport is not responding to any keyboard commands. The clock and meter lights are 'on', but the Record/Memory lights are not 'on'. I have checked and double checked all the connections I had messed with. I found one lead that got a wee bit bent and straightened it back in place. I can only conclude that I did something to cause a failure between the transport and the control PCB..but where?!?!? Maybe I 'stressed' an IC in the control circuit. Did I destroy this nice deck?
I have a lot of test equipment and time. I also have a service schematic which is hard to follow. How should I proceed?
Welcome to Beoworld !
Check the solder joints where the connector for the large white plug is soldered to the regulator board - that's not farfrom the fuse, you replaced.
Martin
Thanks for the reply. I guess you think some continuity has been disturbed. I will get my FLuke 179 On It.
No cold or faulty joints @P-1. Pulled the regulator board out for inspection. All looks OK except for a little darkened area around the emitter leg of IC 1.(?)
Still no response to controls. The capstan motor rotates continuously, but the transport will not rise. There are lights for the counter and meter, but nothing for the control functions.
Could some relays/switches in the transport be causing it to be stuck in auto stop?? Are there other areas/sub circuits one might target for possible failure?
Check voltages from the power supply.
Martin:
Voltages off P5 & P21 all seem acceptable.
P5 (w/motor running) Pin 1 = 12.7, #2 = blank, #3 = 12.7, #4 = -23.7, #5 & #6 = -.01, 37 = 23.4, #8 = 27.27
P21(motor runnning) Pin 1 (blue) = 12.8, #2 (green) = 23.41, #3 (brown) = 2.26
Next??
Thanks for your attention.
Peter
Hi. Thanks for the welcome. I really like my old Beocord 8004. Hoping I can get it back to life!
Does the standby button work ?Any of the number buttons etc. ?
Yes. Standby works. Capstan/reel motor shuts off and comes back on when any other control button is pressed. Also, the counter lights and meter scale lights come on. And, yes, number buttons work, too.
I am perplexed by the constant reading I get from each of the 4 solenoid terminals; 26.6v ?. Whereas, the solenoid supply plugs # 13, #14, #15 on connector P1 read 11.5v, 26.9v, and 11.5v, respectively. (I am obviously unfamiliar with this solenoid based control system having spent a lot more time with Jap decks, especially Nakamichi, that have a very different set up. ) I presume that current is switched from one solenoid to the other depending on the mode chosen on the control panel....and this switching is made possible by IC8 and IC9 on the control board....? Makes me think that I did something to damage these ICs.
Last note -- after reading voltages from the regulator board's strap connectors, all seem acceptable save for a low reading of 10.5v on P1-16, P6-2 and P6-7. Should be 15v as per the manual's schematic specs. I don't know if this is of any significance to the problem at hand. Tracking back on this circuit I do see an indication of 33v @D5 on the schematic and I am getting only a 6.6v reading...hmmmmm
Still confounded,