How to test magnetic heads | Portastudios | cassette multitrackers | erase & record / playback heads

[@zacharybrown1738]

Thank YOU 🎉 doing this for the erase head on my Yamaha MT50 led me to two wires broken off from the solder at the erase head solving my issue of two tracks not entirely erasing the audio (at least I learned about bias oscillators and have new multimeter 😅) ❤ from Oz

[@travisraab]

Can narrowing down dead tracks be done without Dupont wires?

[@Tetrakan]

Yes and no….the point of the DuPont wires is they are the right size to get inside the header - which is typically inaccessible using just your meter probes - then you can touch the exposed end with your meters, that means if you get a beep the internal coil of the head AND the connecting cables are intact. You can do the continuity test using the tiny circuit board at the base of the head, but that doesn’t guarantee the health of the wires running from the circuit board to the header, and half the time those are the problem because the solder is emetic or someone tugged on them when they were in there for an unrelated maintenance or troubleshooting task. So go ahead and test using the circuit board, but also order some male to male DuPont wires off Amazon prime, it’ll cost you a couple of dollars tops, and do the test again from the header once they arrive.

[@lesliemakin]

Thanks and useful info. Need to do this on a Porta Two which is not erasing ch4. I have a spare Porta05 which I might use as a replacement if needed. Time to get the multi meter and magnifying glass out

[@RobbyDanksworth]

Could you also use the continuity test to painfully signal trace? .... trying to find signal loss on my 246

[@Tetrakan]

No. You could only check the tracks between components. Continuity is really just checking if the resistance is below 50 ohms, and beeping if it is. There are a lot of healthy components in an AC audio signal path high will have a resistance above 50 ohms - for example healthy electrolytic capacitors will appear to be open circuit in one direction because they block D.C. in one direction.

[@bobsbits5357]

i never seen wear on any porta studio units i am fixing my MR1 4 TRACK play back only as i have alot of quad audio recording the coils that deal with the recording are bad and can't be fixed the hz coil was on all the time and over heated in the tascam 38 there a 150 khz coil that on all the time 8 pin mk 1 10 pin mk 2 bob

[@jathonholden]

hello, correct me if im wrong, but I believe you're testing the erase head in this video while talking about the rec/play head? The larger plug is usually erase head and the red and white are for rec/play? slightly different wiring on these ministudio teac rec/play heads which will not show continuity no matter what multimeter configuration. any idea how to test the rec/play heads? genuinely interested. thanks for the videos

[@Tetrakan]

Hi, thanks for watching, yes it's the erase heads being tested here, I didn't mean to give the impression it was the rec/pb head, I was talking about heads in general... different heads have different number of coils or gauges of wire in the internal electromagnet, and you're right the continuity beeper won't go off if the resistance of that coil is below 50 ohms, but on my meter at least they still show the resistance: So, for example, rec pb heads in Tascam portastudios have a resistance of about 170 ohms, if one channel shows OL or a much lower value than 170 ohms that's an indication that the fault lies with the head itself. I go into this on more detail in a more recent video kzbin.info/www/bejne/mWOXfqusZpiZbqs

[@jathonholden]

@@Tetrakan Thanks for the reply, I see! Will have a look. Keep up the good work

[@wawazonzon24]

Thank you! I have a 424 with an issue on channel #2 and not the other 3 channels. Intermittent dropouts / low gain. I suspect it's the record/play head now!

[@Tetrakan]

Thanks! But if its passing signal, it's probably NOT the head, which is good news because the heads aren't made any more. More likely there is bad solder or electrolytic capacitors surrounding the playback and/or record amplifiers for that track.

[@shawnlennon1947]

hey I remember you had a video on doing this for erase heads an you spit out a number like 80 something. I dont remember what setting you used on your multimeter, or the unit of measurement but you said that number needed to be that number in order for a healthy erase head to erase and you tested it against the other healthy tracks. I looked through your whole channel and cant find it lol

[@grahamcrackeh]

Channels 4, 5, and 8 on my 488 mkii's erase heads failed the continuity test but also dont record or playback. Is that repairable or would I need to replace the erase head completely?

[@rcary]

Im having an issue with recording side of my Tascam 122b. I have just got it and am servicing it and getting it all nice so i can look at it all day. :D But im having an issue with audio when it comes to recording. Let me explain..... So i hooked up RCAs and played a demo LEFT/RIGHT audio from you tube and listening on SOURCE it plays fine. Audio on LEFT then RIGHT plays back and forth. Silence on the channel without audio, then audio, etc. So the signal going in is fine. Whats happening is when i listen back on REPRO the LEFT/RIGHT audio plays back on both channels. Its not switching back and forth on L/R like when on SOURCE. And if i pull say the LEFT rca plug out i will get silent on the left channel (headphones), but when the right channel plays the audio its on both sides of the headphones. Same thing when i pull the RIGHT rca. Whatever signal its getting its pushing it to both channels. Basically MONO. There isnt any stereo imaging, and the level knobs do the same thing. I cant get separation of the channels. Any ideas whats going on? I have pulled all the plugs and reseated them. Nothing looks out of place. Could the PLAY/REC board have some issues? Im not sure which area to address first. As far as playing tapes, that sounds fine. Heads have been aligned and appear to be ok. Just wondered where a good starting would be, and have you experienced this before? Cheers

[@district01radio]

on my 414 mkii playback is working fine but recording is not. Can this be a problem with the head play/rec head or is it a bigger chance that it has to do with the pcb components? Also the erase head is not erasing.

[@Tetrakan]

If its not recording or erasing on all four tracks, the first thing I'd check is the record tab detection switch in the top left corner of the cassette cavity. Assuming, that is, that tab is still present on the cassette you're recording with?

[@district01radio]

@@Tetrakan Yes the tab detection switch is still there and so is the tabs on the cassette. Channel 2 does record when the gain is maxed out but at very low volume and it distorts and fades out alot. I will test it out with some blank tapes soon. Btw the ALPS 401547 fader can be taken apart and used as replacement parts for the master fader on the 414 in case you ever stumble upon that problem. It is basically the same fader except that its missing the 2 middle pins. But every other part is the same so you can use the fader brush for example since those tend to break.

[@Tetrakan]

Thanks. If playback works, then the issue is not with the head, but the record amplifiers and/ or noise reduction. Low signal could just be poor calibration but Distortion and altered frequency response indicates one or more electrolytic capacitors need to be replaced. With problems on all four channels I'd be inclined to recap that board and see where you are - there's no guarantee that will catch your issue but it is likely and in any case you're adding to the longevity of the unit since those capacitors have rhe shortest shelf life of any of the components in the circuit

[@district01radio]

​@@Tetrakan I have done some more testing. Channel 1 now records with some recording calibration. It erased a little bit better but there was still some of the old recordings in the background. The recording still cuts out too. Could this be a bias issue maybe? I recorded with NR off so I don´t think that´s the issue. All the capacitors look okay and there is no sign of damage. I might recap it either way just to be sure though.

[@seanmcdonald4686]

Do you service cassette duplication equipment?

[@Tetrakan]

No, sorry - I've never had a chance to look at duplicators, plus don't really have time on top of youtube, dayjob, etc.

[@t0nito]

I just found out today that my 3 head TEAC V-2RX tape deck has an open left record coil, it plays alright and records the right channel, but recording the left channel is completely dead, measured the resistance of the record head and I'm getting 128 Ohms on the right channel and completely open on the left channel, I've measured directly on the head and not the wiring so I can rule out a broken wire. It's really a shame because it's a pretty decent deck, but I can't find a new head for it except one imported from the US which they are asking around 200€ for it which is way more than I'm willing to spend.

[@Tetrakan]

That's a shame. Couldn't you use a head from another model though? I've successfully transferred fostex heads into Tascam units for instance...

[@t0nito]

@@Tetrakan Being a 3 head unit the play/record head are actually two small seperate heads stuck together, I've been searching on ebay and the only one I found other than the exact same model is actually quite similar if not physically identical despite being a different brand but also equaly as expensive. I never knew a head coil could actually become open circuit, I've tried resoldering the pads under the head in hopes it was just a bad contact but no dice. Had it been a single head I would just try in a random one and try it out but either I'm not searching correctly or the "double heads" are quite rare.

[@Tetrakan]

Ooft. Happy hunting...

[@shawnlennon1947]

I have a very bizarre erase issue. the tracks all erase and record but track 2 it records the signal low and with a lot of wow and flutter on playback and it also will not erase on that track, just keeps stacking recordings. perfect for someone into making tape loops. NOT ME lol.

[@Tetrakan]

I see from your comment on the video about tracing the bias signal from the oscillator to the head that you found it, so I'm just replying for the benefit of anyone else browsing the comments. What you're describing as wow and flutter is the cancellation between old and new material because erase bias isn't reaching that head to scrub old recordings before new tecordings ate made. The most common cause of this is the little wires at the base of the erase head need to be soldered back on. Its also possible the coil in that segment of the head is open (broken) and you can use the continuity test shown in this video to establish that - a healthy erase head should cause the meter to beep and show a reading of around 13 ohms. If the wires are connected and the head is okay and you're erasing OK on other tracks ( meaning the oscillator is working) the next obvious thing to check would be the relays or transistors which turn the erase on and off for the problem track. You can use a scope or frequency counter to test for the presence of the bias signal downstream of the relay/transistors in record mode - if the bias signal isn't getting past the relay/transistors, replace those components.