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Project/One Mark IV B receiver service manual?

kwayde

kwayde

AK Subscriber
Subscriber
I picked this unit up today and before I looked for a manual I jumped right in replacing the fuse holder then firing it up on a dbt. Lamp dimmed so it went full power and it receives fm stations good but the controls were very dirty.
Noticed the biggest problem was the relay contacts and the fact that it doesn't have the plastic cover. A couple dial lamps were toast and one of the watt meters had the leads snipped.
I ripped it apart and removed the Alps volume control from the board so I could open it up to clean the contacts. Cleaned all controls and noticed some 2sc1400 transistors on the tone board that will be replaced. I finished for this evening.

I did a quick search for a service manual but found nothing. Does anybody know if there's one out there to download, or if there's a comparable one that will work? Once I get it back together somewhat I can check the relay voltage to figure out what to replace it with, but I'd like a manual for setting bias, etc.


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Been doing some reading and found these units were made in the '70's for Playback Audio in Hillside, 20 minutes out from Chicago so there are no manuals to be had. I hate when that happens...
 
kwayde said:
Been doing some reading and found these units were made in the '70's for Playback Audio in Hillside, 20 minutes out from Chicago so there are no manuals to be had. I hate when that happens...
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That's a bummer! I see these listed all the time and I thought about taking the plunge. I thought they look very much LIKE a Pioneer SX-x80 or SX-x50 series receivers, and always assumed they were made by Pioneer and could use one of their service manuals. Have you been able to fix it?
 
jpreza said:
That's a bummer! I see these listed all the time and I thought about taking the plunge. I thought they look very much LIKE a Pioneer SX-x80 or SX-x50 series receivers, and always assumed they were made by Pioneer and could use one of their service manuals. Have you been able to fix it?
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Yes, I did replace the relay and it works fine. One of the watt meters wasn't working so I had to tweak it to get it working. Had to tweak the signal strength and tuning meters to get them to work too. The other watt meter was no good as someone before me got into it and messed it up. I replaced the watt meters with meters from a Pioneer SX model which were a perfect fit.
I have worked on a couple Mark 1B receivers that thankfully only needed the controls cleaned. The one I just finished yesterday has a bad tuning meter, just like the first one I worked on last year. Opened the meter up and tried to get it working but it wouldn't respond. The meters in these units are always failing.
The units I've seen didn't have a major problem to get real involved in. Just dirty controls, burned out bulbs, a bad relay and bad meters.

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kwayde said:
Yes, I did replace the relay and it works fine. One of the watt meters wasn't working so I had to tweak it to get it working. Had to tweak the signal strength and tuning meters to get them to work too. The other watt meter was no good as someone before me got into it and messed it up. I replaced the watt meters with meters from a Pioneer SX model which were a perfect fit.
I have worked on a couple Mark 1B receivers that thankfully only needed the controls cleaned. The one I just finished yesterday has a bad tuning meter, just like the first one I worked on last year. Opened the meter up and tried to get it working but it wouldn't respond. The meters in these units are always failing. The ones I've seen didn't have a major problem to get real involved in. Just dirty controls, burned out bulbs, a bad relay and bad meters.

View attachment 2683635 View attachment 2683640
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Nice! Glad you got it working! I have one I'm going to see this evening. It's the Mark IV B model. The seller told me that one of the channels is "scratchy" but I didn't ask him about the meters (there are four of them in this model). My guess is going to be that they are not working.
 
Hopefully the scratchiness is just dirty controls. Watt meters from Pioneer SX-780 & 880 receivers are a perfect fit but they come as one piece and will need to be separated. The black meters in post #4 are from an SX-780.

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The bulb diffuser looks just like the ones Pioneer used.

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kwayde said:
Hopefully the scratchiness is just dirty controls. Watt meters from Pioneer SX-780 & 880 receivers are a perfect fit but they come as one piece and will need to be separated. The black meters in post #4 are from an SX-780.

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The bulb diffuser looks just like the ones Pioneer used.

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Just picked 'er up! Needs a good cleanup inside and out. Used my dbt and there were no issues. Went ahead and powered 'er up - sounds really scratchy so I used some deoxit. One of the lights is out - most likely I'll replace all three with LEDs.

The tuning meter was working when I was using the FM function. Definitely I'll need to replace the L/R power meters - they're stuck half way and there is no movement at all. Also, there is no movement on the signal meter.
 

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kwayde said:
Yes, I did replace the relay and it works fine. One of the watt meters wasn't working so I had to tweak it to get it working. Had to tweak the signal strength and tuning meters to get them to work too. The other watt meter was no good as someone before me got into it and messed it up. I replaced the watt meters with meters from a Pioneer SX model which were a perfect fit.
I have worked on a couple Mark 1B receivers that thankfully only needed the controls cleaned. The one I just finished yesterday has a bad tuning meter, just like the first one I worked on last year. Opened the meter up and tried to get it working but it wouldn't respond. The meters in these units are always failing.
The units I've seen didn't have a major problem to get real involved in. Just dirty controls, burned out bulbs, a bad relay and bad meters.

View attachment 2683635 View attachment 2683640
Click to expand...
What relay did you use to replace the original
 
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