Tascam 238 Story #2…

[sweetbeats]

Thanks for the additional info.

Parts of the mechanism cleaned/regreased are the reels, capstan bearing, brake levers. Original grease on the head plate is good for now.

So you didn’t disassemble, clean and relubricate the reel table drive mechanism?

I have no idea where the noise is coming from…if it was me I’d be getting out a mechanic’s stethoscope or even using something like a chopstick to my ear and probe around to narrow down where the sound is coming from. But it sounds like it could be the reel table drive mechanism. What lubricant did you use for the other mechanisms? Did you check/adjust the capstan thrust bearing?

The irregular behavior from the supply reel…I only see it happening with that one UDII CD60 tape. Does it actually happen with other tapes? Could it be a problem isolated to that tape?

Secondary motor was pulled out and idler inspected, fairly fresh tire measured 10mm at outer diameter.

Fairly fresh tire…how do you know…? Do you know it’s been replaced or is it possible it’s the original tire? The biggest mistake I feel people make when refurbishing a vintage cassette deck is doing nothing more than putting eyes on the rubber parts, feeling them and if they subjectively see okay chalking it up as good. If the parts are original, they need to be replaced at this point…period. New pinch roller, and I *highly* advise against going the cheapskate route which is doing nothing more than getting a replacement “donut”…get a complete replacement roller, and preferably one from Athan. And get the replacement reel table drive assembly idler from Tascam. I can’t remember if it’s in this thread or not but there’s an updated part number and it was cheap, and they had stock at least a couple years ago. There’s just no point in going to the trouble to pull the transport assembly, tear it down and not go the distance with what should be done if you want it to work right, or at least mitigate potential causes to issues. I’m not trying to be overly critical, I’m just speaking from personal experience you 100% get out of a cassette transport refurb what you put into it, and the rubber components can look and feel okay, but what you can’t see is how they’ve become mis-shaped over time or know without a durometer and the original spec whether or not the parts are actually still good, and there is a small margin of serviceability for these parts. And the bottom line is in 100% of the machines I’ve worked on from the 70s, 80s and 90s, which includes your 238, the rubber components were past service life…every time.

Wondering if other components on the controller board are bad - I didn't have the replacement bipolar caps so left the old ones in, other ceramic caps there seem to be involved in the play control too.

Help me out…what board are you calling the “controller board”? The Control PCB? And what bipolar caps? Give me the part designators…C__ and C__ etc. on what PCB assembly? Ceramic disk caps rarely go bad. The only time I see them fail is if they are in a sustained over voltage condition or high heat condition. That’s not the case here…these are not the droids you’re looking for. And think of it this way…I don’t believe your issue is electronic. In PLAY mode the supply reel is not driven. The tape is precisely driven by the capstan, and the reel table drive mechanism drives the takeup reel to provide takeup tension. In this transport there is no holdback tension at the supply side, it is passive via the friction of the cassette itself. So there’s no servo control or electronic control of supply side holdback tension in PLAY. Your issue is mechanical. There is no electronic drive or control of the supply reel in PLAY. And, again, I’m only seeing your issue with that one cassette, so please clarify if I’m seeing that incorrectly.

The scrubbing seems strange and mechanically related but there's a probability of the controller needing more work.

By “scrubbing” are you talking about the strange noise, or something with the scrub/shuttle function? And, again, I disagree there is any issue with transport control. I think your problem is mechanical.

 

[Tape2]

Thanks for the additional info.



So you didn’t disassemble, clean and relubricate the reel table drive mechanism?

I have no idea where the noise is coming from…if it was me I’d be getting out a mechanic’s stethoscope or even using something like a chopstick to my ear and probe around to narrow down where the sound is coming from. But it sounds like it could be the reel table drive mechanism. What lubricant did you use for the other mechanisms? Did you check/adjust the capstan thrust bearing?

The irregular behavior from the supply reel…I only see it happening with that one UDII CD60 tape. Does it actually happen with other tapes? Could it be a problem isolated to that tape?



Fairly fresh tire…how do you know…? Do you know it’s been replaced or is it possible it’s the original tire? The biggest mistake I feel people make when refurbishing a vintage cassette deck is doing nothing more than putting eyes on the rubber parts, feeling them and if they subjectively see okay chalking it up as good. If the parts are original, they need to be replaced at this point…period. New pinch roller, and I *highly* advise against going the cheapskate route which is doing nothing more than getting a replacement “donut”…get a complete replacement roller, and preferably one from Athan. And get the replacement reel table drive assembly idler from Tascam. I can’t remember if it’s in this thread or not but there’s an updated part number and it was cheap, and they had stock at least a couple years ago. There’s just no point in going to the trouble to pull the transport assembly, tear it down and not go the distance with what should be done if you want it to work right, or at least mitigate potential causes to issues. I’m not trying to be overly critical, I’m just speaking from personal experience you 100% get out of a cassette transport refurb what you put into it, and the rubber components can look and feel okay, but what you can’t see is how they’ve become mis-shaped over time or know without a durometer and the original spec whether or not the parts are actually still good, and there is a small margin of serviceability for these parts. And the bottom line is in 100% of the machines I’ve worked on from the 70s, 80s and 90s, which includes your 238, the rubber components were past service life…every time.



Help me out…what board are you calling the “controller board”? The Control PCB? And what bipolar caps? Give me the part designators…C__ and C__ etc. on what PCB assembly? Ceramic disk caps rarely go bad. The only time I see them fail is if they are in a sustained over voltage condition or high heat condition. That’s not the case here…these are not the droids you’re looking for. And think of it this way…I don’t believe your issue is electronic. In PLAY mode the supply reel is not driven. The tape is precisely driven by the capstan, and the reel table drive mechanism drives the takeup reel to provide takeup tension. In this transport there is no holdback tension at the supply side, it is passive via the friction of the cassette itself. So there’s no servo control or electronic control of supply side holdback tension in PLAY. Your issue is mechanical. There is no electronic drive or control of the supply reel in PLAY. And, again, I’m only seeing your issue with that one cassette, so please clarify if I’m seeing that incorrectly.



By “scrubbing” are you talking about the strange noise, or something with the scrub/shuttle function? And, again, I disagree there is any issue with transport control. I think your problem is mechanical.

Yes, the parts of the assembly to pull the reels out for cleaning : front plate, shaft clip, tape reel guide, spring, brake arms. Then the motor for the idler assy.

Capstan movement is smooth and silent, at the inner capstan shaft base no wear or dirt noticed. It's a floating magnetic design. No issues there IMO.

Lubricants used are Singer sewing machine oil for the capstan shaft, lithium long life grease for others shafts.

Irregular movement happens with all types of tapes tested. On an SA60 too but my camera's fps/definition are too low for the video to make it noticeable.

Idler rubber spec'd good at first but some slippage occurs, whilst not being the only cause of this 238's issues. I agree they all need replacing. This 238 is a potential aquisition, so ordering expensive parts, shipping being twice the cost of the part where I live, is usually done after the unit is deemed to be repairable with reasonable time/financial investment in my case. Generic plumbing rubbers are used in the mean time if I can find them.

The controller board as a short term for the capstan servo control pcb, the one above the capstan, not the control pcb designated in the service manual.

There are electrolytical SMD caps on it that leak, damaging the traces and sometimes other components as you know. The non bipolar caps go bad first being more sollicited on the circuit. The two EL bipolars are C12 and C14. 3.3uF/25V.

Yes the supply side reel is passive. I've now learned there's a magnetic tensioning circuit on both reels though. L1 and L2 coils behind them assist the tape tension. They're fed by the "Joint PCB Assy" which is linked to the capstan servo control board and the sensor pcb . The L1 coil measures at 0.5V on one side instead of around 8V.

For now a defect on this coil is likely to be a cause of the tape jumping, and the idler tire the cause of the scrubbing noise, which sounds like plastic on plastic or metal, never heard a tender/grippy rubber tire making this type of noise. It must have been replaced in the past and I guess it's slipping on the inner tire surface to the plastic wheel.

Thanks again for your input.

 

[sweetbeats]

Thanks for all that info. I think you know more about the system than I do. And yeah I’d ultimately want to replace the non-polar parts on the servo board, but if it’s working it’s working; those caps C12 and C14 filter the power to the motor coils.

There is still a thrust bearing on the capstan shaft/flywheel asssembly…see here:

Right there in the middle of the back of the flywheel.

Those coils off the mechanical joint PCB…interesting. I always thought those had something to do with monitoring the rotational direction of the reel tables. I see your point.

I read back in this thread and the part number for the current and correct reel idler is in a previous post. It was pretty affordable. I know sometimes off-the-shelf parts work for these applications, but that’s not been my experience in more critical applications like the 238 and other similar machines with a scrub function. So I get your point about price and shipping for the part, but it’s what will actually work.

 

[Tape2]

Thanks for all that info. I think you know more about the system than I do. And yeah I’d ultimately want to replace the non-polar parts on the servo board, but if it’s working it’s working; those caps C12 and C14 filter the power to the motor coils.

There is still a thrust bearing on the capstan shaft/flywheel asssembly…see here:

View attachment 149511

Right there in the middle of the back of the flywheel.

Those coils off the mechanical joint PCB…interesting. I always thought those had something to do with monitoring the rotational direction of the reel tables. I see your point.

I read back in this thread and the part number for the current and correct reel idler is in a previous post. It was pretty affordable. I know sometimes off-the-shelf parts work for these applications, but that’s not been my experience in more critical applications like the 238 and other similar machines with a scrub function. So I get your point about price and shipping for the part, but it’s what will actually work.

Hopefully replacing the two bipolars will fix the tension issue, or that would mean a defective coil, or further damage on the repaired capstan control board.

Ok I see, was thinking of a ball bearing not a pressed copper ring like here.

Will check out the tire part number.

Nice clean unit you have there, unlike all the ones around my area !