Teac A-3340 Reel to Reel - Dc power supply section

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AnnieJohnson

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Hi All,
I have recently acquired Teac A-3340 machine and it has 100Hz hum in both playback and recording mode which makes me think that power supply capacitors probably need changing. I opened the unit today and could not locate the power supply components anywhere. According to the manual, both A3300 and A3340 share the same power supply circuit and there are two 1000/35WV caps (labelled as C2 and C3). However I just could not find these components anywhere. I am sure they are in there somewhere.
I have attached a picture of the unit and I would be grateful for anyone (who has worked on this unit before) to help me pin point these components.
Kind Regards
Annie
Teac-a-3340.webp
 
Annie, I suspect the power supply board is the upside-down board in the lower left of your picture. I can probably verify later looking in my document library. Are you sure it's a 100Hz hum? Are you in a 50Hz or 60Hz electric service region?
 
Hi, thank you for your reply. Last night, after my message, I spent a lot of time looking at it again and from what I can tell, its the control board that seems to have the DC power supply section. However the board has 220uf and 820 uf caps (they look original and not changed) and yet the circuit diagram refers to 2 x 1000 uf Caps.

I was looking for 2 x 1000 uf caps all along.

Anyway I will start with these caps to address my 100Hz hum problem.

I am sure it is 100Hz as I have checked it on line out terminals and the hum is always there (when you switch the machine on) although it becomes louder in RECORD mode. I am in the UK and the operating frequency is 50 Hz. If you have any other ideas as to where this 100Hz hum is coming from and how to pin point it further, then I would be really interested to know.

Regards

Annie
 
AnnieJohnson said:
Hi, thank you for your reply. Last night, after my message, I spent a lot of time looking at it again and from what I can tell, its the control board that seems to have the DC power supply section. However the board has 220uf and 820 uf caps (they look original and not changed) and yet the circuit diagram refers to 2 x 1000 uf Caps.

I was looking for 2 x 1000 uf caps all along.

Anyway I will start with these caps to address my 100Hz hum problem.

I am sure it is 100Hz as I have checked it on line out terminals and the hum is always there (when you switch the machine on) although it becomes louder in RECORD mode. I am in the UK and the operating frequency is 50 Hz. If you have any other ideas as to where this 100Hz hum is coming from and how to pin point it further, then I would be really interested to know.

Regards

Annie
Click to expand...

Hi Annie
This..http://homepage.ntlworld.com/lez/Teac A3440/Teac A3440_a look at the circuitry.pdf
might help!

Could be the 1000muffs but could equally well be a faulty regulator circuit. I don't know what the current draw is on the 24 volt rail (have you checked the voltage btw?) but I would guess it is well under one amp and so if the regulator is borked I would just replace it with a 7824 chip.

I have had a 3440 for many years but it has never showed any fault save a capstan belt. I am lucky since although I am an electronics tech of 68yrs I would find the machine a pig to work on!

Best of.

Dave.
 
Hi Dave,

Thank you for your prompt response and for the attached document. My background is also electronics engineering but over the years I have moved on to software development and testing, although I still restore old electronics hardware etc. I must admit I have mainly worked on AKai reel to reel decks and this is the first Teac I have acquired. I was not very impressed when i opened it yesterday. I think a lot more thought went into Akai design where a proper modular approach was used and different sections of the deck could be easily separated by the use of clean and straightforward connectors. However in Teac, there aren't really any connectors; just too may wires going back and forth and directly soldered here and there.

Anyhow, I will carefully go through the attached pdf that you sent.

Thanks again

Regards
Annie
 
You are very welcome.
I have had a read through it. I see near the end he shows a design for "pro level" output amps?

Much better performance will of course be got from an NE5532 these days if you need +4dBu from a very lowZ.

Dave.
 
Hi All,
Finally I changed all 4 caps on the control board as well as both diodes but I still hear the same hum….
I think there is a voltage regulator (marked D317) there too which may be the same as LM317T (adjustable voltage regulator). Please correct me if I am wrong.
Also measuring the DC voltages on this regulator (D317), I see the following:
Voltage on Adjust terminal of D317 = 33.8V
Voltage on Input terminal of D317 = 37
Voltage on output terminal of D317 = 37V
I have no way of knowing what the correct dc output voltage should be. Does anyone have any details they can share with me?
Thanks again
Annie
 
AnnieJohnson said:
Hi All,
Finally I changed all 4 caps on the control board as well as both diodes but I still hear the same hum….
I think there is a voltage regulator (marked D317) there too which may be the same as LM317T (adjustable voltage regulator). Please correct me if I am wrong.
Also measuring the DC voltages on this regulator (D317), I see the following:
Voltage on Adjust terminal of D317 = 33.8V
Voltage on Input terminal of D317 = 37
Voltage on output terminal of D317 = 37V
I have no way of knowing what the correct dc output voltage should be. Does anyone have any details they can share with me?
Thanks again
Annie
Click to expand...

Sorry Annie, I cannot find D317 on the circuit I sent you.
I am pretty sure the 24 volt supply to the audio is on the PSU PCB and is done by Q's, 601, 602, 603. Is there 24 V on tag 8 of that PCB? If so I would suspect C603 to be sugered or the 1000mic C602.
R 601, 1.5R is only rated at 2watts so the current cannot be more than 1.7A and I would say a lot less than that since it would get bloody hot! Is Q 602 on a heatsink? I suspect not. You could rebuild the regulator circuit but I don't have the transistor types availabe and sourcing them could be a trial. I don't even know the voltage of D610 the Zener.
I would just pull all the transistors and wire in a 78/24 in place of Q602. A bit of heatsinking never hurts!

If you get really stuck Annie I can check some stuff in my machine but you will have to give me a day or so to get at it!

Dave.
 
Hi Dave,
Thank you again for your message and suggestions. I checked the manual in detail and realised that it was actually a transistor (2SD317), not a voltage regulator. The transistor was removed and checked and found to be busted. Luckily I had some TIP41a around which are pretty close match to D317. Replaced the transistor and then it was magic (no hum and everything was as it should be)

Now I have the task of re-aligning all three heads as someone seems to have messed with them in the past.
Again, thank you to everyone for their help and suggestion.

To summarise, my problem was 100Hz hum on playback (louder when in record mode). The problem was mainly due to faulty D317 transistor on the control board but I changed both diodes (full wave rectifier) + 4 capacitors on the board.

Regards
Annie
 
Reeesult!
With regard to the head alignment problem. I have had my machine from brand new and know the heads have never been touched. If you like I could make you a test tape.

Does your machine have "simul-sync"? If so that makes the record head alignment a lot easier.

Dave.
 
Hi Dave,

This is fantastic news, thank you for the offer of a test tape. I think that would really really help me a lot.

Yes the machine has "simul-sync"? but I dont know how to use it for head alignment.

I managed to align Erase head last night (before proper alignment, it was not erasing properly and i could still hear some audio left on one of the channels after erase)

However record and playback still need alignment and I dont have any reference tape to play first in order to align these heads.

Please could you give me some info on how simul-sync may be used for head alignment?

Regards

Annie
 
AnnieJohnson said:
Hi Dave,

This is fantastic news, thank you for the offer of a test tape. I think that would really really help me a lot.

Yes the machine has "simul-sync"? but I dont know how to use it for head alignment.

I managed to align Erase head last night (before proper alignment, it was not erasing properly and i could still hear some audio left on one of the channels after erase)

However record and playback still need alignment and I dont have any reference tape to play first in order to align these heads.

Please could you give me some info on how simul-sync may be used for head alignment?

Regards

Annie
Click to expand...

Ok Annie, but let me be clear as to what I am offering!
I can certainly record some tones on my machine, specific frequencies on specific tracks at any level you chose but it would be a MANUFACTURED test tape, any headware will be built into the results (tho they LOOK fine) . A commercial 1/4" 4 track TT would be hard to find I would guess and far from cheap.

I have never aligned a 4 track OR machine, done scads of cassettes (I could see then mind!) . Aligning a record only head is a PITA because you can only read from the downstream replay head and the delay is very offputting. With a sync machine you just set it to play!

I am sure there will be some recorder tech's here that can talk you thru the methodology? How much test gear do you have? Essential I would say is a decent audio millivoltmeter, FSD better than 10mV. Scope would be most handy.

Dave.
 
Hi Dave,
Thanks again for your message. It would be good to know how to use sync technology to hear from the record head that may help with alignment.

As for test gear, I have a low frequency signal generator (which can generate sine wave and different frequencies (1K, 10K, 15K etc) and an oscilloscope but I really need to understand how to use these to align record and playback heads.

If someone can explain the procedure to me , then it would be really helpful.

Thank again for your offer.
Regards
Annie
 
Thank you arcaxis.
Can I once again put out a request for the 12 pin rectangular plug used for the remote control? I have the remote built and working but it is plugged in via panel pins!

Dave.
 
arcaxis said:
Is it the one that looks like this one on the Tascam RC-71 that I'll likely be selling in the near future? :)

I bought this for my 246 Portastudio years ago and before buying it I tried to build a plug. The remote itself was easy, but not the plug. I may have done something like you with panel pins, but ultimately bought the right stuff.
Click to expand...

Aha! It's a moulded unit! Maybe that is why I could not ever find one? The plug, as a component might never have existed.

Anyways, the setup works and the machine never goes anywhere so I am not going to drop any dosh on a remote box! In fact since my son has gone to France It is not used at all. I am no musician and I think tape has had its day. (ooooer!).

Dave.
 
ecc83 said:
Does your machine have "simul-sync"? If so that makes the record head alignment a lot easier.

Dave.
Click to expand...
how so? EDIT .. never mind .... I see it's been explained

I have a 3340 and a 2340 ..... they both still work well but I know I'm gonna have to start doing some stuff to them so I'm compiling info in preparation of that.
And the remote plug for my 3340 is round ...... a model change?
 
ecc83 said:
Reeesult!
With regard to the head alignment problem. I have had my machine from brand new and know the heads have never been touched. If you like I could make you a test tape.

Does your machine have "simul-sync"? If so that makes the record head alignment a lot easier.

Dave.
Click to expand...


Hi Dave,
I hope you are well. I was wondering if you or someone else here is in a position to do a quick test for me. I am nearly there with my tuning but with the lack of original test tape, I want to align playback output as close as possible to the actual value.

If someone can check the following and let me know, then I would be really grateful.

1. With an input signal of 0dB (at Line input) and MONITOR switches at SOURCE position, how far do you have to wind up INPUT LEVEL controls before you see 0dB on UV meter? Are the input level controls knobs at say 2 O’clock position, or 3 O’clock position? I just want to know the rough position.

2. With the same input signal (INPUT level of 0dB on VU meter) recorded on a tape, when you play it back, how far do you have to wind up OUTPUT CONTROL knobs to get 0dB on VU meters (during playback)? In other word, when the same 0dB signal that was applied to the input and was recorded is NOW playing out at 0dB (on VU meters), where are the output control knobs positioned? Are they roughly at say 2 O’clock position, or 3 O’clock position? I just want to know the rough position.

Thanks in advance
Kind Regards
Annie
 
Hi Annie,
It will be a day or so before I can get my machine working (I don't use it you see) and I can certainly do as you ask.

However, it is usual when speccing a machine to have all the controls at maximum and to feed in specified levels.

Are you feeding the front mic/line jacks or the rear RCA connectors? And do not forget we have different tape recorders!

Dave.
 
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