I'm working on my first reel to reel-a teac A4010SL. I got it to play by taking apart & clean / Lube where needed. My problem now is that when recording its output is low & has popping noise whenever bass will hit in both channels. The source input is perfect just problem in record. The unit has been sitting about 20 years according to previous owner. Anyone know of any common fixes for record circuit on these?
Hi gto127. what tape are you using? could just be that you need vias setting for the low output, as far as the popping noise goes- are you sure you are recording at the correct level, you may be recording too loud which causes distortion.
i haven't done a record bias alignment in years but as memory serves it does requires a scope and a pre recorded set of test tones. odds are something's gone south in the record bias trap.the popping your referring to:does it seem like bass transients kick (drum,heavy bass)are trying to break through to a normal volume but don't.. that would be an indication of record bias problems.
i assume in the refurbish process that you've de-magnetized the heads and guides.
i assume in the refurbish process that you've de-magnetized the heads and guides.
Yes this sounds like bias issue to me, I have a newer version of this deck the A-4300SX.
Before messing with any of the bias adjustments first check with a scope to see if the bias oscillator is actually running.
If it is not than it probably is just a bad transistor.
Meanwhile exercise the high and low bias level switch, they may need to be cleaned after the unit has been setting a long time.
Bad switches can also cause this sort of experience.
The Bias Switch adjusts the bias level between two levels of bias for using of different tapes.
The Level switch that is next to the bias switch only adjust the level of audio signal, I think that it is for the High End Playback EQ, Actually I believe this switch only effects the meter calibration (I don't remember it do both), This can be verified in a service manual that can be found here,
TEAC A-4010GSL Manual - Stereo Tape Deck - HiFi Engine
It has been quite some time since I messed with my collection of old Teac machines as they all need new capstan belts and don't work.
But I do these type of alignments every once in a while on my more mordern machine the Tascam MSR-16 and Otari MTR-12 and MTR-15.
I also have a couple of 4 track Teac's as well, I just love the sound of analog tape machines.
Once you get it working it is possible to tweak the machine easily since it is a three head setup but you do need a signal generator and a scope.
You can't really trust your average DMM because they do not measure with a flat response, they are only good for 50/60hz and maybe up to 400hz or so.
I few that I have, have been accurate to 1khz but above that forget it unless you have one that specifies that it is good the the whole 20hz to20Khs audio range.
Test tapes are not cheap but do start with a good HQ tape when making these adjustment's.
Good tape can sometimes be found on Ebay but you can get a very excellent freshly made tape from ATR Magnetics, I use this tape now and it is most excellent!!
It is basically the only tape that you will find anymore and they will ship right to your door,
1/4″ Master Tape | Product Categories | ATR Magnetics
There are a quite few websites that go into great detail on this alignment process.
jer 🙂
Before messing with any of the bias adjustments first check with a scope to see if the bias oscillator is actually running.
If it is not than it probably is just a bad transistor.
Meanwhile exercise the high and low bias level switch, they may need to be cleaned after the unit has been setting a long time.
Bad switches can also cause this sort of experience.
The Bias Switch adjusts the bias level between two levels of bias for using of different tapes.
The Level switch that is next to the bias switch only adjust the level of audio signal, I think that it is for the High End Playback EQ, Actually I believe this switch only effects the meter calibration (I don't remember it do both), This can be verified in a service manual that can be found here,
TEAC A-4010GSL Manual - Stereo Tape Deck - HiFi Engine
It has been quite some time since I messed with my collection of old Teac machines as they all need new capstan belts and don't work.
But I do these type of alignments every once in a while on my more mordern machine the Tascam MSR-16 and Otari MTR-12 and MTR-15.
I also have a couple of 4 track Teac's as well, I just love the sound of analog tape machines.
Once you get it working it is possible to tweak the machine easily since it is a three head setup but you do need a signal generator and a scope.
You can't really trust your average DMM because they do not measure with a flat response, they are only good for 50/60hz and maybe up to 400hz or so.
I few that I have, have been accurate to 1khz but above that forget it unless you have one that specifies that it is good the the whole 20hz to20Khs audio range.
Test tapes are not cheap but do start with a good HQ tape when making these adjustment's.
Good tape can sometimes be found on Ebay but you can get a very excellent freshly made tape from ATR Magnetics, I use this tape now and it is most excellent!!
It is basically the only tape that you will find anymore and they will ship right to your door,
1/4″ Master Tape | Product Categories | ATR Magnetics
There are a quite few websites that go into great detail on this alignment process.
jer 🙂
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You don't need a reference tape to calibrate recording (bias, level and EQ). Reference tape is required only for calibrating playback (level, frequency response) and for playback head alignment.
I think that a machine which has been sitting idle for 20 years needs a more thorough checkup. I would look for dry capacitors, bad/oxydized trimpots and relay contacts. Electronics revision should go along with mechanical overhaul.
That said, the problem you describe comes from faulty electronic part, rather than from calibration.
I think that a machine which has been sitting idle for 20 years needs a more thorough checkup. I would look for dry capacitors, bad/oxydized trimpots and relay contacts. Electronics revision should go along with mechanical overhaul.
That said, the problem you describe comes from faulty electronic part, rather than from calibration.
i always start by ensuring the playback head is ok and that it's capable of playing something that was recorded/dubed on another machine (nothing worse than a machine whose heads are aligned to each other but not to other machines) to ensure the problem isn't just just mis-alignement between the heads. i also use a dub of a test tone and try to erase it as a means of assessing bias level if the tone or a faint distorted version of it can be heard at the repro/playback head then yes it's into troubleshooting from there.
Hello everyone,
Sorry for late reply. I never got a email that I had any responses. Thanks for all the ideas. I did look at the record relays and don't see any way to open. The contacts do look okay from what I can see through the plastic. I did clean but haven't demagnetized the heads. I will give that a try. I did find a few suspect caps & replaced but made no difference. I did notice if I record with no signal that previous recording is not being fully erased. I'm using the Scotch tapes that were recommended for machine. Tapes that were previously recorded on this machine years ago play fine as well as factory recorded tapes.
Sorry for late reply. I never got a email that I had any responses. Thanks for all the ideas. I did look at the record relays and don't see any way to open. The contacts do look okay from what I can see through the plastic. I did clean but haven't demagnetized the heads. I will give that a try. I did find a few suspect caps & replaced but made no difference. I did notice if I record with no signal that previous recording is not being fully erased. I'm using the Scotch tapes that were recommended for machine. Tapes that were previously recorded on this machine years ago play fine as well as factory recorded tapes.
I would first get a service manual or schematics. First thing to look at would be the heads, the flat polished gap in the middle should not exceed 3mm, otherwise the heads are used. Next, check the oscillator circuit which feeds the erase head. It is a HF signal in the range of 100 kHz and several tens of volts which "rasterizes" the magnetic coating. You will surely find trimpots on that module for each channel and for each speed. This is where you set bias and they might be bad. Try turning them either way while recording without signal to see if you attain erasing depth.
But I would again advise for a more systematic approach, starting from the PSU and related voltages and checking every module step by step.
But I would again advise for a more systematic approach, starting from the PSU and related voltages and checking every module step by step.
Yes, I've cleaned heads and downloaded manual. Think I found the problem. Variable caps in bias circuit. Cleaned both with Deoxit. This fixed one side but the Deoxit destroyed the other. I've run into this problem with Deoxit before and thought it was isolated but now I'm done using it on any pots. The shack don't have variable caps so hopefully mouser will. Thanks for all the ideas & tips on this thing. It's a surprisingly good sounding piece especially for age.
Having problem finding the trim caps I need. Ebay or mouser doesn't have these. Anyone know a source? They are 20-200 pico adjustable. They are flat rectangular about half inch by 1/4 in wide.
I think this one should do just fine provided that the voltage rating is OK:
GMC40300 Sprague Goodman | Mouser
GMC40300 Sprague Goodman | Mouser
That probably would work but they have minimum purchase of 44 which I would I would not be able to do. Thanks for link.
Just thinking what if I measured value of the good trim cap then replaced it with by passed film caps to produce same value. Would that work or is there something special about these trimcaps?
Variable capacitors are there for purpose, obviously for adjustments. Again, I reckon you are stumbling in the dark because looking at the manual or schematics would answer your question.
I have the manual. I was referring to making the adjustments with the good trimcap. Measure the calibrated value,replace it with film cap then adjust other side with good trim cap.
You just cannot do that, otherwise the machine would be factory adjusted and fitted with fixed value capacitors instead. Can you tell us where are the varicaps located, in which module or circuit, and how do alignment instructions mention them?
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