😂I agree completely with the previous writer! Just bought the complete restoration kit on E-Bay and waiting for the delivery as also for a divice to test condensators and so on wathever is on the board to find of my REVOX Mark III. Thank u indeed so much the same and lets find out everything. This morning I unscrewed the impossible bolt near the motor just with a thin, long screwdriver ticking it around anti clockwise before I had it oiled a bit. It’s an adventure…
Your video is the best tutorial to service! Too much details! Thansk you so much. I will try service the power supply and speed board on my MK II, but I'm afraid because the cables faded the colors, dirty and hard. I need label everything firstly, as you did.
That power supply pcb is a pain in the ass. I cut all original smooth wires and create extension with proper copper stranded wire. Double insulation on every junction. The original smooth copper wire has coating that must be scraped with exacto knife in order for solder to grab.
I think the hardest is the mainboard (the board where the cards slot in). I have not done it yet and thinking of doing it with video to help others. The PS board with the info in this video looks straight forward.
@@vitezmiroslav1389 4 track is more mainstream, 2 track is more headroom and zero crosstalk. 4 track is half the tape length. So you decide according to your expectations. If you want to record own music 2 track. If you want to listen to music and record existing material to listen to, 4 track.
on the pins as showed on 28:26 put meter with positive on the top first pin and negative on the 3rd. Generally, from the top, the first 2 are +21V, the next 4 are ground, next 1 is open and the next 4 are +27v. Very clearly shown on the document on the link on the description of the video.
I just removed the board I just want to share with you that I found a very easy way to remove that screw in the back , I just used a pointed screw driver and knob off the post from its base and it come out attached to the screw , very easy . Thank you to share your video !
I remember doing this service to mine years ago. I resorted to removing the entire assembly, transformer and all. It was like removing the transmission from a car, heavy and clumsy getting it out and back in. I took so many pictures and made so many drawings to make sure it all got back together right. That trimmer pot on mine was in bad shape, so I replaced it and adjusted it to spec after the machine was running again. That was a good 8 years ago or so, never had a problem with it since then. Replaced all the electrolytic capacitors as well as those problematic film capacitors on the transport control board, the ones that go up in smoke. Still plenty I could do to it, its really a pleasure to work on and use. Thanks for the video.
I'm trying to fix the problem myself I'm not a technician but I can replace parts and try my luck ,the capstan motor is not working so I replaced all 3 boards new and still is not working where should I start looking now , I adjusted the pot to 21vDc on the power supply but shows 32 vDc where it should be 27 v Dc .the fast forward and rewind works not the capstan motor .
Can be bad motor, damaged tacho sensor or else. Tou have to check tacho sensor signal. check motor for open circuit. Did you replace power supply board? Did tou check the motor capacitor?
Yes , new power supply board , speed board and 3 new motor capacitors , Thank you , your video help me a lots doing that ,I'll check the tacho sensor @@dchatz
Great video, this will help a lot. When recapping it, there’s a few electrolytic capacitors which are hard to get. Did you buy it through Nagravox or was it cheaper to buy on your own?
Generally I bought all elect.caps at my nearby store. Some values are not common, mainly 25 or 250uF but do put 22 or 220uF instead which are common without worries. If you want to be accurate (which I think makes no difference) you may put 22+2.2 instead of 25 and 220+22 instead of 250. Generally getting the closest existing value is a safe choice.
Take all the preamp cards out. Check again. If it fails check the diodes on the 2 solenoids. If OK then you need further check by a technician. If you can fix electronics yourself you have to start checking all the components on the power supply board and then proceed to check which line has a short.
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😂I agree completely with the previous writer! Just bought the complete restoration kit on E-Bay and waiting for the delivery as also for a divice to test condensators and so on wathever is on the board to find of my REVOX Mark III.
Thank u indeed so much the same and lets find out everything. This morning I unscrewed the impossible bolt near the motor just with a thin, long screwdriver ticking it around anti clockwise before I had it oiled a bit. It’s an adventure…
Your video is the best tutorial to service! Too much details! Thansk you so much. I will try service the power supply and speed board on my MK II, but I'm afraid because the cables faded the colors, dirty and hard. I need label everything firstly, as you did.
That power supply pcb is a pain in the ass. I cut all original smooth wires and create extension with proper copper stranded wire. Double insulation on every junction. The original smooth copper wire has coating that must be scraped with exacto knife in order for solder to grab.
could you send me pictures of that service with the cable wires?
I've repaired and restored 5 of these. Removal of the PS board is the hardest part of it.
I think the hardest is the mainboard (the board where the cards slot in). I have not done it yet and thinking of doing it with video to help others. The PS board with the info in this video looks straight forward.
Great video, thanks. Just to the point.
I did not find 20 kohm potentiometers. Maybe 22 or 25 kohm? Thank you.
@@vitezmiroslav1389 22k is totally fine
@@dchatz Thank you
@@dchatz Which is better, 2 or 4 track? Thanks
@@vitezmiroslav1389 4 track is more mainstream, 2 track is more headroom and zero crosstalk. 4 track is half the tape length. So you decide according to your expectations. If you want to record own music 2 track. If you want to listen to music and record existing material to listen to, 4 track.
greetings Is the Tektronix 2225 good? Thank you.
@@vitezmiroslav1389 I don't know. Sorry
Great video and well explained my capstan motor won't move how and where I plug the meter to check for 21 v Thank you
on the pins as showed on 28:26 put meter with positive on the top first pin and negative on the 3rd. Generally, from the top, the first 2 are +21V, the next 4 are ground, next 1 is open and the next 4 are +27v. Very clearly shown on the document on the link on the description of the video.
@@dchatz That’s great thank you I’m watching your video how to service the speed control board , I may need do that next .Thank you
@@dchatz I need to have the machine connected to power with the jumper on right?
@@imsaint007 yes
I just removed the board I just want to share with you that I found a very easy way to remove that screw in the back , I just used a pointed screw driver and knob off the post from its base and it come out attached to the screw , very easy . Thank you to share your video !
Thank you too
Just did the same this morning, lol😂
Hello, I have a question. The revox a77 has a 25 kohm potentiometer, can I install a 22 kohm? Thank you.
@@vitezmiroslav1389 sure. I also did that. 25 kohm pots cannot be found now
@@dchatz How many volts does it have to be? Does it adjust with it? Thank you.
@@vitezmiroslav1389 yes. And it must give 21v. Adjust it to about 21.4
@@dchatz Thank you very much.
@@vitezmiroslav1389 beware. I see that mine is 2.2 and NOT 22kohm
I remember doing this service to mine years ago. I resorted to removing the entire assembly, transformer and all. It was like removing the transmission from a car, heavy and clumsy getting it out and back in. I took so many pictures and made so many drawings to make sure it all got back together right. That trimmer pot on mine was in bad shape, so I replaced it and adjusted it to spec after the machine was running again. That was a good 8 years ago or so, never had a problem with it since then. Replaced all the electrolytic capacitors as well as those problematic film capacitors on the transport control board, the ones that go up in smoke. Still plenty I could do to it, its really a pleasure to work on and use. Thanks for the video.
I'm trying to fix the problem myself I'm not a technician but I can replace parts and try my luck ,the capstan motor is not working so I replaced all 3 boards new and still is not working where should I start looking now , I adjusted the pot to 21vDc on the power supply but shows 32 vDc where it should be 27 v Dc .the fast forward and rewind works not the capstan motor .
Can be bad motor, damaged tacho sensor or else. Tou have to check tacho sensor signal. check motor for open circuit. Did you replace power supply board? Did tou check the motor capacitor?
Yes , new power supply board , speed board and 3 new motor capacitors , Thank you , your video help me a lots doing that ,I'll check the tacho sensor @@dchatz
Thanks alot for the PDF shematic of power supply board . I am recapping my A77 HS - about 45 years old .
A77"HS". Rare and nice, I would like to have a HS version but they are rare.
Did you have to remove the solenoid and/or motor to get to that screw ?
No, all this effort was to finally avoid removing anything else. And it suceeded.
I first take out the 2200uf 50v cap. First remove the leads. I use a 3" screwdriver.
thx it is the best video for this section for the A77 thx so much
Glad to help.
Great video, this will help a lot. When recapping it, there’s a few electrolytic capacitors which are hard to get. Did you buy it through Nagravox or was it cheaper to buy on your own?
Generally I bought all elect.caps at my nearby store. Some values are not common, mainly 25 or 250uF but do put 22 or 220uF instead which are common without worries. If you want to be accurate (which I think makes no difference) you may put 22+2.2 instead of 25 and 220+22 instead of 250. Generally getting the closest existing value is a safe choice.
@@dchatz Thank you
Thank you very much for your work nd sharing it with us.
thank you too for your support. On future video there will be a speed control board service
Pls Just tell me how can I repair my power supply only when I put new fuses n switch on the burns internal lower only
Take all the preamp cards out. Check again. If it fails check the diodes on the 2 solenoids. If OK then you need further check by a technician. If you can fix electronics yourself you have to start checking all the components on the power supply board and then proceed to check which line has a short.