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Tinman
Super Member
It could be any number of things from a shot of deoxit, which everyone hopes is the fix in a can, to bad capacitors which is far more common in Revox gear.
Sadly, the C270 is rare and I won't work on it because of "no parts". But I'd check all fuses, re-seat the cards and connectors, and have a good look for FRAKO and RIFA capacitors.
THOSE are usually the prime cause of trouble with all Revox gear.
Sadly, the C270 is rare and I won't work on it because of "no parts". But I'd check all fuses, re-seat the cards and connectors, and have a good look for FRAKO and RIFA capacitors.
THOSE are usually the prime cause of trouble with all Revox gear.
Hi AMR2,
the 0.47uF caps and the partially hidden resistor should not be there according to the circuits I have for the beast. Check the value of the Motor Run cap on it's own and see if it is in spec (8uF for both motors on my drawings). Extra components here are not a good idea as the motor power is controlled by a PWM square wave at 76.8 kHz. The transients around such circuitry should not, in my opinion, be messed with!! I have 2 of these machines and neither one of them has extra components here.
The tension roller near to the tacho regulates the power to the dragged motor by position. The pulling motor is fed a power setting from a D/A converter which the CPU decides on mode of operation.
There is also a comparator on the tension roller which enforces STOP if the roller approaches the lower end of it's travel. This is seen by the CPU as a Tape Break. So if the motor control on the supply reel is iffy then the supply tension may not be able to be controlled. The eratic motion in your video looks like the comparator is being triggered when the roller drops low.
At this moment in time I would be concentrating on the capacitor to get back to as per Studer.
Keep us posted.
GPS16
the 0.47uF caps and the partially hidden resistor should not be there according to the circuits I have for the beast. Check the value of the Motor Run cap on it's own and see if it is in spec (8uF for both motors on my drawings). Extra components here are not a good idea as the motor power is controlled by a PWM square wave at 76.8 kHz. The transients around such circuitry should not, in my opinion, be messed with!! I have 2 of these machines and neither one of them has extra components here.
The tension roller near to the tacho regulates the power to the dragged motor by position. The pulling motor is fed a power setting from a D/A converter which the CPU decides on mode of operation.
There is also a comparator on the tension roller which enforces STOP if the roller approaches the lower end of it's travel. This is seen by the CPU as a Tape Break. So if the motor control on the supply reel is iffy then the supply tension may not be able to be controlled. The eratic motion in your video looks like the comparator is being triggered when the roller drops low.
At this moment in time I would be concentrating on the capacitor to get back to as per Studer.
Keep us posted.
GPS16
amr2
Well-Known Member
Yes, you are right, those components are not in the schematic. There are two motor run caps, and those Rifa and that resistor are only in one of them. I’m going to remove these extra components, check the main caps, and see what happens. Thank you very much, I will keep you updated.
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amr2
Well-Known Member
It seems that that resistor and those caps were there from the beginning. Perhaps a service bulletin? the resistor is wired to a support, and from there goes the cable to the control board. See attached pic:
With new caps the unit seems to work again. and also without those extra components.
The motor caps are not bad:
The Rifas are a “little” out of specs
There are some more Rifas in the control board. I will change them.
I’m going to do some more test, but seems that it has come back to life
With new caps the unit seems to work again. and also without those extra components.
The motor caps are not bad:
The Rifas are a “little” out of specs
There are some more Rifas in the control board. I will change them.
I’m going to do some more test, but seems that it has come back to life
Tinman
Super Member
Imagine THAT! Another Rifa! You know, a little epoxy to seal up that crack... good as new.
Yeah, while you have the machine open, find them all and replace. I'd go after any Frako caps sooner than later, except the giant power supply one's for now. Those seem pretty robust.
Buuuuut....... the deck is well fused, and as long as YOU are your own tech... it's a judgement call.
When I do one for a customer, I only want to do it ONCE, so it all gets changed.
Yeah, while you have the machine open, find them all and replace. I'd go after any Frako caps sooner than later, except the giant power supply one's for now. Those seem pretty robust.
Buuuuut....... the deck is well fused, and as long as YOU are your own tech... it's a judgement call.
When I do one for a customer, I only want to do it ONCE, so it all gets changed.
