Not that old
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Negative.Power lost for good now. Troubleshooting. I get power on the two blue and two white wires leading to diodes D601 and 604 but nothing on F2 and F3. Difficult to reach the diodes for measuring.
Technics RS-1500 FF and REW do not stop
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Not that old
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Power supply now rectified and in order. I now get 5V out from TR608 to D-connection pin 2. After that I don't know what to do.
My "expertice" limits stop around here. Badly need help.
FF and REW still cannot be stopped.
Now that you fixed the 5V problem, we can start to follow the transport button signals through the logic control to see if we have a bad chip.
Its purpose is to maintain the last logic state of the input signals. In the case of IC1, when you press the FF button, a 0v signal is input to the latch which "sets" it. When you press STOP, the 0v input on the other input "clears" the latch. All IC1 is doing is holding your input button press until the next button press comes along.
- Find connector B on the board. (It is shown on the board layout towards the top of the board)
- This is the input from the Key Switch board.
- Pin 4 (green highlight) goes to the FF logic.
- DMM set to measure VDC, black lead clipped to chassis ground
- Red lead on Connector B, pin 4 (FF)
- Measure the voltage when the button is not pressed, then again as you press and hold the button down
- You should probably get something like =5V (not pressed) and 0V (pressed and held down)
- Next, we will try the REW button
- Connector B, Pin 6 is the REW button
- Do the same test with button not pressed down, then again as you hold the button down
- Measure the two voltages on Pin 6
- This will test to make sure that the buttons are working OK and the signal is getting to the control board.
- If all of that looks good, we can jump to the output connector "D" and check the signals.
- Connector D, pin 4 (I think) should be 5v when you pressed the FF button, then go back to 0v when you press the STOP button.
- Same with Connector D, pin 3. It should do the same for the REW button.
- Let me know what you find out.
Its purpose is to maintain the last logic state of the input signals. In the case of IC1, when you press the FF button, a 0v signal is input to the latch which "sets" it. When you press STOP, the 0v input on the other input "clears" the latch. All IC1 is doing is holding your input button press until the next button press comes along.
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dhnash
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I believe this should be pin 3.
I think I fixed them all.
Not that old
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Thank you the great help. Unfortunately I am out of action for a few days (hospital) with no access to the 1500. Hope to start troubleshooting in a few days.
Not that old
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Thank you
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While I am out of action, I would like you to clarify this.I have taken for granted that I should take mesurements to chassis. I asked ChatGpt about that and was told that is wrong. The yellow rail Gpt mentions, is the yellow wire from the transformer to the pin on the power supply. Quote "A quick question. I thought that pin2 (5V) on connection D should be measured from pin to chassis. In reallity it measures from pin2 to YEW rail. Why is that? " Unquote
Looking at the schematic, it looks like they are tied together, but it is not explicit.
If you want to be sure of where to attach the test lead, look at the board schematic and find the connector pin that is connected to the dark black ground line.
Here is what AI says:
I don't have wire colors on my schematic (do you) so I don't know what "YEW rail" means. If you are referring to the transformer secondary center-tap, then there are two as shown in the schematic and both are connected together presumably tied to the common, or ground trace on the boards.
At some point on one of the boards, this signal is tied to chassis ground.
You can easily verify if chassis ground is connected to ground with power off (unplugged) and checking continuity between the chassis and one of the ground pins on a chip or connector on the board.
Does this look like your Power Supply Board or is it different. In doesn't match the board layout in the SM for the transformer connector?
This has 10 wires, but the layout in the SM has only 8 wires?
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Not that old
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Seems we have some differences in the inputs from the transformer. I have no color codes on my WD either. The YEW wire is acc. to Gpt be my ground wire.
When I use chassis as ground, I get no meaningful values. Maybe the black one beside YEW is part of the Y-prong shown on the WD. My WD shows no figures/values around
the transformer area.Sitting on a hospital bed and hunting down text and pictures right frome Onedrive, so I hope what I write makes some sense anyway.
I will hopfully sit behind the 1500 soon.
Attachments
It sounds like your transformer to PS board is wired like this. I'm not sure how your two meter lamps are connected?
To connect ground to the chassis, there might be a black wire or board trace that gets connected to the chassis on one board. You might need to have the board mounted to the chassis to connect to the chassis for ground to the other boards.
- BLU = 11.7V
- WHT = 34V
- ORG = 28.5V
- BLK/YEL = Common/GND
To connect ground to the chassis, there might be a black wire or board trace that gets connected to the chassis on one board. You might need to have the board mounted to the chassis to connect to the chassis for ground to the other boards.
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OK, back in action again.
I did the measurements you suggested and got these results:
Conn. B pin 4=4,9V when FF not pressed. 4,9V when pressed (no change). Pin 6=4,9V REW not activated. 4,9V when activated (no change).
Conn. D pin 4= 4,9V when not pressing FF. 0V when pressing. Pin 3= 0V when pressing REW. 4,9V when not pressing REW.
For your info, PSU voltages across the BLU wires is 19,5VAC - ORG = 46VAC - WHT = 55VAC. Per pin I get these values: ORG 1 & 2 = 23VAC
WHT 1 & 2 = 27,8VAC - BLU 1 & 2 = 9,5VAC.
What can I do next?
Something does not seem right. When you push either the FF or REW button, pin 4 (or 6), Connector B, should go to ground (0v) as long as you hold the button down.
But you measured a change for both the FF and REW signals on the output connector D when you press the button so it is doing something.
Check pin 2 of connector B. It should be 0v or ground then double check pins 4 and 6.
With power OFF, you can use your DMM to check continuity of the FF and REW switches.
But you measured a change for both the FF and REW signals on the output connector D when you press the button so it is doing something.
Check pin 2 of connector B. It should be 0v or ground then double check pins 4 and 6.
With power OFF, you can use your DMM to check continuity of the FF and REW switches.
- One probe on Connector B pin 2 and the other on pin 4.
- You should read an open or high resistance
- Press and hold the FF button down and you should read close to 0 Ohms until you release the button.
- Do the same with the REW button. This will make sure that the buttons are OK.
- While you are at it, check to make sure that the STOP button is functioning the same.
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Not that old
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I have measured again and I get this:
Connector B pin 4=4,9V. Pressing FF=4,9V. Pin 6=4,9V. Pressing REW=4,9V. Pin2=0V
Connector D pin 4=4,9V. Pressing FF=0V. If I now press STOP I get 4,9V. Pin 6=4,9V. Pressing REW=0V. Again STOP shows 4,9V.
FF and REW keep running whatever I do. No reaction from the STOP button except when in PLAY. Must be shut off by tension arms or power OFF.
Continuity between B2 and B4: FF=2ohm. REW=OL. STOP=OL. I don't really understand the two OL.
Let me understand what you are measuring:
- With power OFF, NO buttons pressed, when you measure resistance from Conn B Pin 2 to Pin 4 you get 2 Ohms (FF button)
- Same conditions as above, Conn B Pin 2 to Pin 6, you get OL (means over "Over Limit"... resistance too high to measure) = Open connection (REW button)
- Same conditions as above, Conn B Pin 2 to Pin 1, you get OL (STOP button)
It could be on the Key Switch board or the button is stuck in the depressed position.
Between the other two tests, it reads OL because the button is not pressed so the signal path is "Open".
You can test this by measuring the resistance between Pin 2 and Pin 6 (OL), then press and hold the REW button. The reading should go to 0 Ohms.
Same with the STOP button.
You can test the other buttons in the same way, continuity from Pin 2 to the appropriate button. Should be OL (open) when not pressed, 0Ohms when pressed.
If this is all true, then we need to figure out what is bad.
Can you post a photo of the front and back side of the Key Switch board?
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Not that old
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The Key Switch Board is a fixed part of the unit as far as I can see, but I am attaching a photo (not very good) of the back side.
I rechecked the measurements and this time think I got it right.
Connector B pin 2 to 4 = 0,9ohm. Pressing FF = 0,2ohm
Connector B pin 2 to 4 = 0,9ohm. Pressing REW = 0,9ohm
Connector B pin 2 to 4 = 0,9ohm. Pressing STOP = 0,9ohm
Connector B pin 2 to 6 = 1 ohm. Pressing FF = 0,2ohm
Connector B pin 2 to 6 = 1 ohm. Pressing REW = 1ohm
Connector B pin 2 to 6 = 1 ohm. Pressing STOP = 1ohm
I'm not sure how to find the correct button connection.
Attachments
I'm a little confused. Here is your photo of your Key Switch board. It looks like there are two sets of 6 connector pins. Is there a cable that attaches to each or are there wires on the other side of the board? Which connector and which board do the wires connect to?
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The two sets of pins plug into the Main Control Board. As far as I understand the other side of the Key Switch Board contains the actual pushbuttons.
All buttons work as such, but the STOP button signal does not reach FF and REW. Works OK in PLAY.
I am checking the MCB, but no joy.
Where do they plug in, both only have 6 pins each.
I was reading another post on tapeheads and the suggestion for transport problems was to replace the 9 electrolytic caps on the Main Control board. You could start with that and see if it helps.
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