Reel to reel repair - Page 1
Forum section: electronics / repair

author: payty
author_rank: Contributor
timestamp: May 13, 2025, 05:13:55 am
content: Hello everyone!I am trying to repair an old reel to reel player.So far I have managed to get it work, except for the recording function..There is an oscillator, made with two transistors and a transformer that makes an alternating current used both for erasing head and recording head.The thing is that it does not even erase the tape. The sine signal goes to the erasing head, measured directly on head wires (~50V), the erasing head shows ~5Ohm resistance, the tape runs over the erasing head but ....it s not being erased. All heads have been cleaned, so dirt is out of question.Connector XS1 goes to the erasing head, XS2 to the recording head.Any ideas what I might check? It s driving me nuts because I cannot find the cause.Could the erasing head be bad even if it shows some resistance on the multimeter?Thanks!

author: RoGeorge
author_rank: Super Contributor
timestamp: May 13, 2025, 07:30:02 am
content: Have you tried with a different brand of tape? (I vaguely remember a cassette that after many years untouched, it remained permanently magnetized, though other different tapes from the same age were erasable, no idea why).If the tapes are OK, maybe the erase head has internal short circuited turns, or it has some other mechanical failure.If both coils of the erasing head measure about the same, then it is probably not the erase head's fault. Try to measure the head inductance, too. I've measured out of curiosity an erasing head (not from Rostov), and each coil measures about 1.2\$\Omega\$ and 81uH, with all the wires disconnected.Another easy thing to do is to replace the electrolytic capacitors related with the erasing oscillator, they usually dry out after decades.Double check any mechanical switches and connectors in the path of the erasing oscillator and the wires to the erasing head. The 50V at high frequency might be just induced signals from a single wire (with no current in the erasing head).

author: Runco990
author_rank: Frequent Contributor
timestamp: May 13, 2025, 07:08:46 pm
content: I'm going to ask the blatantly obvious question, as I have absolutely seen it before:Did you have the tape the right way around touching the head? Yes....people have done this and ran a flipped tape. Erase failure is quite rare.

author: Paul Price
author_rank: Super Contributor
timestamp: May 14, 2025, 03:15:18 am
content: Clean the gap in the erasing head face that tape runs past.

author: Pentium100
author_rank: Frequent Contributor
timestamp: May 15, 2025, 08:03:17 am
content: 50V should be enough or the erase head.1. Does the erase head affect the tape at all? I mean if the erase current is not enough, the erase head should still damage the high frequencies on the recording.2. Is the erase head height correc? Do not touch the screws, just check if one of the tracks is on the top edge of the tape. The tracks of all heads should line up. Aligning the height is annoying so do not disturb the screws, just check. Most likely the height is correct, but it does not hurt to look.3. The tape recorder is stereo. Do both channels behave the same (no erase)?4. Is the tape actually touching the erase head?5. Does the tape deck record incoming signal?

author: jwet
author_rank: Frequent Contributor
timestamp: May 16, 2025, 05:35:24 pm
content: You've gotten some good guidance. One thing that I didn't see mentioned:Higher performance tape (Cr02, etc) use a higher bias level and different EQ. Higher bias level tape runs the erase head signal at a higher level since the tape has more remanance. Check a couple of things. If the recorder has a bias setting or a Cr02/Std setting, play with that. If it doesn't, make sure your tape isn't something special that needs a really high bias. In your circuit, I see reference to 9 and 19 and this may be bias level- I don't speak German so I can't really figure out the labels. These signals also go through a lot of relays- that are further controlled by switches. De-Oxit what you can and make sure that all that stuff lines up. If you've got a working bias oscillator putting out 50v, you're close. 5 ohms DC does sound right for an erase head- the bias frequency is ultrasonic usually so the AC impedance is what really matters. The 5 ohms tells you its intact at least.Good luck

author: Pentium100
author_rank: Frequent Contributor
timestamp: May 17, 2025, 11:51:29 am
content: It's a R2R tape deck, unless OP got his hands on the somewhat rare EE tape or something weird like reslit VHS tape, all R2R tapes are what you would call "normal bias" for cassette.The erase head, even if not fully erasing the signal should at least damage it. Even bias signal from the record head damages the previous recording (if it was not erased for some reason).

author: payty
author_rank: Contributor
timestamp: May 17, 2025, 10:04:45 pm
content: Many thanks for all these answwers and advices.While reading all these, and as I ve ran out of ideas, I ve thought....why not check for misalignment of the heads....I have pushed the tape with my finger and ...surprise...it.worked, the tape has been erased. I have replaced the erasing head but never touched the screws that are used for tuning. Just one that keeps it in place but it is sepparate from the others.And recording/erasing was not working anyway even before replacing anything, so I suppose that someone might have messed up the alignment before.So many thanks again!

author: Pentium100
author_rank: Frequent Contributor
timestamp: May 18, 2025, 03:13:51 am
content: Since you have replaced the erase head, you have to align its height. The upper pole should poke out beyong the edge of tape by 0.15mm.This is or a tape deck that also has reverse play head, but you can ignore that.There is a more complicated and precise way to do it, but this should be enough.