TEAC 80-8 Reel Motor Grinding and Pinch Roller Problem

Sweetbeats, I just meant reading the voltage should be simple. I believe you that this can get very complex very fast so I will certainly throw in the towel if I get to a point where I simply cannot go on. Also, I realize you are taking your time to offer free help to a stranger, and I am extremely appreciative (this goes for both of you). Please, if at any point you do not have time to spare and must abandon the thread, I fully understand.

I took the readings. On the supply motor, I saw the same bundle consisting of a red, yellow, orange and brown wire coming out of the motor as on the takeup motor. I measured the voltage across the orange and red wires on both sides. Here's the results:

Supply Motor: 106v REW
63v PLAY

Takeup Motor: 105v FF
75v PLAY

The service manual shows that the motors should be at these voltages:

Supply Motor: 100v REW
65v PLAY

Takeup Motor: 100v FF
80v PLAY

So, assuming I took the readings correctly, these seem pretty decent. What do you think?
 
I think so!

So that’s great. What I would do is consider whether A. the brake is binding (i.e. the brakes need adjusted), and/or B the motor is mechanically bound up (i.e. foreign matter in the windings impeding rotation, bearings needing lubrication or needing replaced). You should be able to manually release the brakes with the machine powered OFF and the motor should spin freely. It has some rotational mass because of the windings et al, but with the brakes released you should be able to spin it up by hand and at should keep spinning (coasting) for a bit in its own. Check that out and report back.
 
With the brake solenoid plungers pushed in, neither reels will "coast." They will turn if I turn them, but as soon as I stop applying force they stop turning. Am I doing something incorrect?
 
Can you verify the brakes are fully released? Is there any difference in the drag between the two motors or do they both feel the same?
 
Like are you trying to spin the motors or just turning them? Are they too resistive to turning that you can’t spin them? Maybe do another video?
 
I found a thread from 10 years ago or so of someone with a similar transport problem. I copied what they did- adjust the takeup brake solenoid positioning- and the takeup reel will now spin in FF (with a little help). This video shows me testing it all. Not sure if PLAY is functioning properly though.

I will say, when I first followed your directions and turned the reels by hand while the brakes were released, the supply side spun a little more freely than the takeup side.

Also, the tension arms on this are slightly different than those on my Tascam 38 and 48, so I think I am threading the tape along the tape path properly, but the tension seems very high so I could have something wrong. There's a video with the tape threaded here.
 
In all these decks you need to have experience to work on them effectively. The Pinch roller solenoid should not be taken off of it's position otherwise the pinch roller pressure must be adjusted using a spring scale or digital bike scale which is what I use. This is why I now take the plunger fork off and then leave the solenoid where it is unless I see signs of tampering.

The noise from the brakes is due to dried out pads. I tell people all the time to replace them like I do here but a lot do not listen- dried brake pads will only damage tape and drum. I bought 3 square yards of felt that I cut brake pads off of. I had already used up 2 square yards already.
The motor that do not have tubes do not need oil as they have ball bearings in them. IF the deck was subjected to liquid spill or moisture the core of the motor can have rust or corrosion making its diameter greater and then it rubs. Make sure reel table is not against the face and then push brake plunger in and release brake that way then you can turn it. So fat in 46 years of working on these I have never had to replace a single bearing but one day it is coming as nothing lasts forever.

The oil I use on the capstan bearing and motor is AMSoil that I found is the best oil possible- it is a car motor oil 0W30 and the Signature series type. It give wow and flutter specs in some deck lower than new decks.

I can answer some question about these as I have two of them in my car now
 
The last two video show error with the tension arm switches- the transport is not to operate if the tension arm is down at 3 o'clock.
The right reel show the tape bending at the outer side which mean the reel table is pushed in too far- the tape is suppose to pack exactly in the center of the hub and never be rubbing on the reel flange on either side. There are lock nuts on the reel table mount to the motor shaft that can be loosened and the adjustment made. There can not be compared with Tascam 38 or other as this is a 1980's design.
 
There is no foreign material with the brakes they need to be changed- how many times do I have to say that? The pads get dried and will not work like they are suppose to- this is a decay of materials and no amount of adjustment will make the difference. It is like trying to use a broken belt- don't be stubborn on parts that need to be changed- change them or you make more headaches for yourself. 1.5mm thick felt is easy to obtain I buy mine on line and they ship it to me.

Power supply caps are due to be change out of this 1980's vintage machine- that was a long time ago. This machine was in the Rack at Teac Factory Service when I started working there in 1982. We used to service cards there. This was in Arlington Heights IL.
 
When Brakes are released form the drums and the contact to the drum is eliminated- this is not always the case due to bent up brake bands, the motors and their reel table should spin freely and keep going a while when you let go of them. If not you have a reel table up against the face- a very common shipping damage case- it just needs to be loosened and position correctly- I am sure I have done thousands of them by now. If the motor themselves are binding then they need to be taken off the chassis and taken apart- this may be more than you want to get into. I have at time taken the brake drum off to check for such problems and in one motor I did find a gouge on the rotor that after many years started to corrode and started rubbing. I sanded it down and put some oil on it. Put the motor back together and it worked fine. Sometimes it take extra time and effort to fix a part. It can be done.
The feed to most reel motors of the AC kind comes off a tap of the primary of the power transformer. I have been shocked by 120 many times in 46 years and I am still here. In Radio I worked with Plate voltages of up to 10,000 volts and for sure I kept my hand out of there. You have to know where to be careful. After 40 Vdc and AC, it is best to know what you are doing in there.
 
Thanks Skywave! I adjusted the reel table height and the reels spin freely now with the brakes released. I will get myself some felt to replace the pads.

Regarding the transport controls- I had to replace the small plastic tension limiter and the microswitches. I can see the plungers on both switches being pressed down and engaged as the tension arm is raised, or in other words the transport controls still work even when the microswitch's plunger is not pressed down. So perhaps I wired it up incorrectly...? The microswitch for the capstan seems to be working properly.

The only other mechanical issue I'm having now is getting the reels to spin properly in PLAY mode. FF and REW works fine, but they struggle in PLAY. Here's a video. I thought maybe it was due to a sticky tape path, I've done an initial cleaning and saw no improvement but could probably clean more thoroughly (which I plan to do before returning this machine to its owner). FYI, I have not done the pinch roller pressure adjustment process yet.
 
I would do the pinch roller adjustment before doing anything else. And what kind of tape are you using?
 
In those videos I have Ampex 456 that seems to not be shedding, but I also have a brand new reel of SM-911 that I'll use from now on to be safe.

When I begin the pinch roller pressure process, I'm noticing that the pinch roller stops spinning with even the slightest bit of pull away from the capstan. Also, the capstan shaft feels pretty smooth, perhaps I need to follow the resurfacing procedure I've seen Skywave describe in other threads.
 
Ok, I'm definitely beginning to suspect the pinch roller pressure is the source of the issues when the machine is in PLAY. The pinch roller pressure seems to be very low, even though I have positioned the solenoid to the extreme end corresponding to what should be the maximum pressure according to the service manual. Am I missing something here, [MENTION=79692]sweetbeats[/MENTION] [MENTION=130918]skywaveTDR[/MENTION] ?
 
The solenoid of a pinch roller should not be at extremes. In fact if you do not have a fish scale or a digital bike scale which is what I use now, then you do NOT have correct pinch roller pressure- understand that as the tape amount changes on the reels the different torques are going to affect the speed differently.
The rolling sandpaper method is used a lot in my shop- yes it is a pain to do but it get results. I suppose I could find someone with a bead blasting machine but that would just add to the cost and time delay.
The capstan shaft should not be smooth or the tape when engages due to higher take up torque will slide through the speed regulating components. If you can push a pinch roller so that it stops with your finger then you certainly have it set wrong. According to 5.2.2 of the manual the specification is 7 lbs of force or about 3.1Kg. This is measured with a wire wrapped around the shaft behind the roller and pulled in the opposite direction of capstan shaft.
 
I do have a spring scale of the type recommended by sweetbeats. I suppose I am confused because the pinch roller SHOULD be at maximum pressure based on where I have put the solenoid, but as you have said I can move the pinch roller by hand when the machine is in PLAY so the pressure is obviously way too low. If they would help, I can provide pictures/videos of the front of the machine, or the pinch roller assembly since I have the back of the unit off
 
Update: Like a fool, I put in the fork holding the pinch roller solenoid plunger backwards when I reassembled the pinch roller assembly a week or two ago. I swapped that around, and everything works great now. I replaced the VU meter bulbs and am officially done with this part of the restoration. Now, to see if the darn thing will even record...
 
Annnd it will play back, but not erase or record. I'm going to follow some suggestions by Skywave in old posts, and check the erase bias level and the J3 jack first. Another thread indicated that some bad ICs were the culprit. I don't have an oscilloscope though, so this may be where I soon have to throw in the towel...
 
Another update: I now have an oscilloscope. I checked to see if the bias signal was making it from the master bias oscillator to the connector J211. Here's what I got, it's a very high frequency low voltage signal. Does this indicate the bias signal is ok, or no? (assuming I used the scope correctly. the ground clip is on the chassis holding the PCB)

And here is a good PDF of the service manual if it helps anyone
 
thedudleys said:
Another update: I now have an oscilloscope. I checked to see if the bias signal was making it from the master bias oscillator to the connector J211. Here's what I got, it's a very high frequency low voltage signal. Does this indicate the bias signal is ok, or no? (assuming I used the scope correctly. the ground clip is on the chassis holding the PCB)

And here is a good PDF of the service manual if it helps anyone
Click to expand...

Cannot dld the manual but you should have several volts of bias. Usually good practice to 'poke' circuits with a X10 probe on the scope to avoid disturbing circuit conditions, got one?

Dave.
 
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