DA-88 back tension

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sweatybetty

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DA-88
Hello all, new guy here. I normally work on analog decks but I had a customer bring me 3 DA-88 decks that are in various needs of repair. I have yet to get one to record and play back. Hoping someone can give a little advice.
The main problem Im having is 2 of the decks are eating tape. Ive narrowed it down to not enough back tension. If i apply a bit of pressure on the supply side tape guide, the tape stays in the guides and feeds properly. Without that pressure, the tape is all over the place.
Is there a back tension adjustment? I do have the FSM but dont see anything in it concerning this.
video here

thanks all sb
 
Verify the back tension arm on the left side of the transport is swinging out when tape is threading and supplying back tension.
 
wkrbee,
I was hoping you would reply!
I found that the tension arm was seized, I thought I had it cleaned enough but I didnt. It wasnt free enough to engage the rotating cam, now fixed. It appears that a screw through a hole on the side of the transport is for a fine adjustment of the tension, correct?
I now have one of the decks working properly but with occasional dropouts in playback. I have cleaned the head and head brushes which helped quite a bit but not completely.
I have 3 decks to attempt to fix or for parts to get one working but I think I can get 2 in working condition. My customer is shickled tit-less that one is up and running.
One of the A/D boards is not working. Do you have a trick for checking the power supply with the board in the deck?

thanks again sb
 
Your best option is to get the Service manual to tell you how to setup back tension. The A/D PCB is powered from the D/A PCB. Check the soldering on the 78xx and 79xx regulators on the D/A/ card.
 
wkrbee,
Thank you.
I now have 2 of them working good. I did find one of the 7805 regulators bad. Pulled one from another card that was missing channels 5 & 6, and it now works. The tension problem is cured. I set the tension by adjusting the set screw until the tape-eating stopped, then another 1/4 turn.
I also found signs of battery leakage on 2 of the sys-con boards, replaced the batteries, checked the traces, all good.
About the only problem i have now is drop-outs on both the working decks. Im hoping its the tape (Maxell XR-metal)
The customer did leave me a few Sony DARS-113MP blanks, Ill give one of them a try.

Thanks again sb
 
Last edited:
Maxell XL is one of the worst tapes to use. The tape was formulated with a abrasive on it to keep consumer 8mm video recorder's heads clean. The best proven tapes were Sony DTRS 60 min and Fujifilm.
 
I did get a Sony tape formatted this afternoon and am going to try some recording tomorrow.
I appreciate the help
 
I think the problems are solved. Recorded some music on the Sony tape, very few drop-outs, and only in the first 8-10 minutes of the tape. This seems to go away after the deck has been run for an hour or so.
Once again, thank you for the help!
 
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