[help] Trouble with Revox B215 cassette

[Patlamm]

Thanks SaSi. Yesterday, i've knock myself out ;-) with the ajustement. Starting with the tape leader sensor, i've just note the original position and then play with the ajustement from one extreme to an other. Although it did make a difference for the tape lead, I cannot say that it change something for the RW/FFW symptoms.

I did the same with two ajustement for the reels, just to see with the extremes, it didn't change the behavior of the machine at all. I'm now wondering what are those ajusments for :-| strange no?

 

[SaSi]

If adjusting the reel photosensor trimmers doesn't make any difference, then I am almost certain, that these trimmers are dirty and the rotating lead isn't making good contact with the graphite rod. I had the same issue myself. Only after cleaning them with Deoxit or equivalent, did they start to make a difference when turned. And only after cleaning them thoroughly, did adjustments become more "linear" rather than "erratic".

Correct adjustment of the tape sensor will not make any difference on the FF/REW.

If you are planning on removing the motor control PCB for cleaning, I would recomend that you take a few pictures of the PCB and closeups of the trimmers, so we can understand what trimmers there are there. I remember in a previous post that someone mentioned that there are more trimmers on the PCB. Are there?

 

[Tinman]

Thought I'd bump this as I just got 2 B215's. I got lucky, though. ZERO head wear on both, one runs so far, and has no issues at all. The other won't come out of stand-by.

Time to pull the schematics out.

 

[SaSi]

Do you have schematics? The Revox service manual only has a block diagram.

 

[Tinman]

Sasi, it's on the Studer/Revox FTP site. Has the schematics.

 

[SaSi]

Patlamm, now both Tinman and myself are proud owners of a B215. (Tinman has two, so I'm jealous). Perhaps we can now help you with your's and the problems in a better way.

If you read the other thread Tinman started you will read I've had similar problems like yourself for a little. It might be what you are having - if you haven't figured out yet what was wrong.

 

[Tinman]

SaSi, it's very interesting. So what you say is, it's possible that even if the sensor for the end of the tape is not working, the tape can stop at the end because of the sensors on the motors. So because of the not working sensor light, there is some missing information for the system to work properly.

See the picture below, on mine, the red light is not visible.

Well, coming backto this, on both my decks this LED is indeed visible red.

I did read that the early version of the B215 was infrared, and the second edition uses the visible red LED. So this is normal. It should also mean you have the version II deck.

 

[SaSi]

Tinman, what S/N are your units? Mine is 007801 dated 27 SEP 1985 (or something like that as the last digit is almost wiped out).

 

[Tinman]

007861 and 015251 for the good one.

 

[SaSi]

7861? Pretty close s/n to 7801 for mine. I verified it was made in Sep 85, as the transport has yet another sticker stating 3.sep.1985

 

[Tinman]

Well, I fixed the second B215! It had a bad record board and only one channel worked for playback.

The culprits were:

A shorted 220uF 10v capacitor next to the right most Dolby IC on the Dolby board pulling down that chip and with it the right channel.

A shorted 100uF 25V capacitor on the record board, across one of the voltage rails.

I replaced both on each board.

Works like a charm.

The moral of this story? You can bet that THESE little buggers are also failing. It's not just gold FRAKO caps anymore.

 

[SaSi]

Good for you. Your failed deck has a s/n very close to mine. So I guess I might have the same problem soon.

But there is a downside for fixing it. Instead of having a good unit and a donor one, you now have two working units and a scratched front panel to think about. Before you know it you will be looking for a dead one in good cosmetic condition and then realize you can fix that too. It never ends.

 

[Tinman]

Good for you. Your failed deck has a s/n very close to mine. So I guess I might have the same problem soon.

But there is a downside for fixing it. Instead of having a good unit and a donor one, you now have two working units and a scratched front panel to think about. Before you know it you will be looking for a dead one in good cosmetic condition and then realize you can fix that too. It never ends.

Oh, you are right.... it's a never ending circle. But I HAD to fix it just so I KNOW I have a good parts donor..... and it has PERFECT heads.... and....
there is a dead one on ebay right now.... and.... :screwy:


I am soooo re-capping the "good" one, though.

 

[steerpike2]

Earlier, I made mention of ball races for the B710 and B215 winding motors (OEM Portescap 23L21-208).
RS Components now also has ball races:
part number 612-5745, cheap at 2 Pounds per pair.

(Depending on how you plan to mod the motor, the 8mm o/d ball race might be appropriate too: 612-5739)

http://uk.rs-online.com/web/search/...=searchProducts&searchTerm=612-5745&x=19&y=17

They also have the tape-guide ball-race for the B77/PR99, cheap:
Part number: 286-784 (this is the same SKF 626-2Z as supplied by ReVox themselves)

 

[steerpike2]

I've acquired a B215 and had problems with the end-of-oxide sensor. Here are some facts I've discovered - in case anyone else wants the info.
The original LED was an infra red device, OP-160SLA made by TRW. 925nm / 1.9mW/cm^2 , operated at 15mA
In 1986 this was revised, to an ESBR3401 made my Stanley, wavelength 660nm (visible red) and luminous intensity of 60 (I assume mCd), with an additional trimpot to adjust the LED drive current.

Panasonic cassettes all seem to have opaque leaders - at all wavelengths - changing from IR to red hasn't helped here.

I've done some tests and the phototransistor is sensitive to green LEDs as well, so if one wanted that 'look', a green LED can be used too. The green LED seems to give the greatest change between oxide/leader. Some oxides are partially transparent to IR, whereas they all block green 100%.

The TDK cassettes with black timing bars create a problem too - the B215 keeps mistaking these timing bars for oxide start - even with an IR led.

The B710 using the IR led does not have problems, so the way it interprets the end-of-oxide signal must be handled differently.

 

[Patlamm]

I've read the new post. It's interesting. I still have the same problem with my B215, i guess it can be the IR sensor because the way the deck behave is very different from cassette to cassette. Sometime it can FF or FR with no problem, and for another cassette, it's a pain in the rear ;-)

 

[steerpike2]

I still have the same problem with my B215, i guess it can be the IR sensor because the way the deck behave is very different from cassette to cassette. Sometime it can FF or FR with no problem,

Well here are some other things I just discovered with mine:
(1) the 2 switches that detect when a cassette is inserted, were not reliable. Wiggling a cassette even a small amount could make it stop. Sometimes the vibration of the cassette during FF or REW was enough to open the switches and make it stop. I used emery paper on the switch contacts.

(2) Try putting a piece of card in front of the IR led, to force it to think tape is always present. This will test to see if that LED and phototransistor are working OK or not.

(3) On mine - as I received it - the IR led was putting out light (verified with a CCD digital camera) but not enough light to activate the phototransistor. It can rarely happen that LEDs lose intensity but still work dimly.

(4) I tried a new IR led - I chose one with an 850nm wavelenghth to be closest to visible light. But it was not reliable - some tapes are too transparent to IR. I changed it to red, and it works perfectly.

(5) the Adustments for the other 4 photo-transistors (R15-R18) have no effect at all for most of there rotation - the oscilloscope trace does not show any useful variation. Up to the point - almost fully counterclockwise - where the output from the phototransistor disappears altogether, then the transport stops. So I just set them midway.

(6) the paper-thin blue-ish coloured 'printed circuit board' that goes to the IR led will not stand more than one unsolder-and-resolder. It is too fragile. Finally I cut it away and just used very thin wires directly from the LED to the brown "flexiprint"

(7) The service manual figures of <1V for tape and >4V for leader are for the ReVox test tape. They do say that you may not get these voltages on all tape types, and to adjust the sensitivity to be symmetrical on either side of 2v for whatever tape you are trying to adjust it with.
With my red LED, I get 5.5V for leader, and around 0.25V for tape, for every cassette I have tried so far.

 

[Patlamm]

//// QUOTE: (1) the 2 switches that detect when a cassette is inserted, were not reliable. Wiggling a cassette even a small amount could make it stop. Sometimes the vibration of the cassette during FF or REW was enough to open the switches and make it stop. I used emery paper on the switch contacts.

/////

It looks like we've found the problem, it does exactly what you said when I wiggle the cassette. Depending of the cassette casing shape, the switches are not pushed far enough, and the contact is poor. If I put masking tape on the switches, the problem goes away. What type of emery paper did you used?

 

[perryinva]

You probably don't need emery. Any fine wet/dry paper, like 1000 or finer will clean them fine. I found on one of mine that the extended brass contact arms on the tape type detect just needed to be bent down slightly so the switches just need a small amount of pressure to operate. You have to remove the face plate to do this, and then they are wide open for your needle nose plier. Be careful putting the faceplate back on, as the clearance of the switches to the faceplate is very tight. I'm not sure about access to the pin switches through the back plate. Maybe some contact cleaner?

Thanks so much for the sensor info! I have one older one with the non-visible and one newer with the visible. I prefer the non-visible. Did you ever find a source?

 

[steerpike2]

Thanks so much for the sensor info! I have one older one with the non-visible and one newer with the visible. I prefer the non-visible. Did you ever find a source?

This is the one I'm currently using (visible red) which I found to be the most reliable of all the ones I tried. LMW32WG - datasheet -

Because the Panasonic cassettes have an impervious leader, I decided to use red rather than IR. I could not find any IR LED that gave as good results. The red one is not very visible - especialy once a cassette is inserted.

I agree too about bending the cassette sensor switch blades - a good idea to make them more reliable. I used 1200-grade aluminium oxide paper; as said, any really fine wet& dry paper will work.

On the B710 there is a solenoid that locks the cassette in during fast wind - strangely they left this out on the B215. The B215 - even though it was very expensive - seems to be made on a much tighter budget than the B710.