Teac A-3340S schematics?
- Thread starter ofajen
- Start date
Thanks! I have the service manual, but no schematics. Unfortunately, I also don't have a parts list. Actually, what I need now is a part!
I completed the playback and monitoring part of calibration on the A-3340S, but just as I was finishing up the "minimum input level setting", where you calibrate the input monitor setting, I accidentally damaged one of the record amp card trimmers while adjusting the monitor level. The trimpot came apart and now, of course, passes no signal. So, channel 4 doesn't pass audio to the output in source setting, though the meter works fine and audio passes in tape setting. A parts designation would be helpful, as would a source for the part!Cheers,
Otto
witzendoz
Senior Member
I still haven't had a chance to look for schematics yet, but I found this site with a service manual:
http://www.roland-vintage-audio.com/MANUALS.htm
http://www.roland-vintage-audio.com/MANUALS.htm
Thanks. I do have the service manual and it does not include schematics or even block diagrams for the cards. It does have detailed service instructions.
I managed to gently desolder the remnants of the trimmer I damaged on my A-3340S. It seems to indicate a value of 33 KOhms, which is not a particularly easy value to find in a particular style and size. I will be happy with a trimmer that is horizontal mount, vertical adjust from above, if necessary. Mouser has trimmers like that in the same size, but the closest values are 25K and 47K. I may get a few of each and try one out and see if it causes problems. Shouldn't be a big deal, since it only affects source monitor volume, not the meter reading, nor anything to do with playback.
Cheers,
Otto
Dr ZEE
Anti-Pro Circles Insider
I have a-3340s machine but don't have schematics. I only have a-2340sx schematics scans, you can d-load zipped file of them here: http://www.mzentertainment.com/studio_workshop_technical_archive.html.
Just want to share a though.
It looks like all three trimpots of the record ampl. section together with associated capacitors and resitors "form" the load network for the Q302 stage of the amplifier. So I would guess, even though Monitor CAL pot adjustment only affects the output level in SOURCE setting, but if you change the resistance value of that potentiometer you may upset the levels over the other two pots: Record Meter and Record. I don't know how "dramatic" this would be, and, maybe even this happens, then only you would need to do after is to recalibrate the channel again from the start.
If I was facing this situation, and I could not find the exact value of the pot, then I would get the pot of closest value below the original and I would add a resitor in series with the pot to compensate for the difference. So, for example, if the original value is 33K, and I have 25K pot, then I'd add a resistor in series of the value closest to 8K that I can find.
Now, it's easy to say, but to actually practically to implement this (to fit on the board etc) can be pain in the neck.
So, this is just a though, and maybe you don't need to worry about all this. You can just replace the pot with what ever you get and see how it works out.
Drop a not after you've done this and how it worked out.
Attached Here is edited cut from simplified circuit of 2340sx, to illustrate what I was talking about. Also I am attaching scan of pots positions, just in case. I was not sure about which exactly pot did you break, as in 2340sx 33K pot is actually Record CAL pot, but it does not fit your description, (there must be some differences betweeen 2340sx and 3340s, but they are very similar machines).
Just want to share a though.
It looks like all three trimpots of the record ampl. section together with associated capacitors and resitors "form" the load network for the Q302 stage of the amplifier. So I would guess, even though Monitor CAL pot adjustment only affects the output level in SOURCE setting, but if you change the resistance value of that potentiometer you may upset the levels over the other two pots: Record Meter and Record. I don't know how "dramatic" this would be, and, maybe even this happens, then only you would need to do after is to recalibrate the channel again from the start.
If I was facing this situation, and I could not find the exact value of the pot, then I would get the pot of closest value below the original and I would add a resitor in series with the pot to compensate for the difference. So, for example, if the original value is 33K, and I have 25K pot, then I'd add a resistor in series of the value closest to 8K that I can find.
Now, it's easy to say, but to actually practically to implement this (to fit on the board etc) can be pain in the neck.
So, this is just a though, and maybe you don't need to worry about all this. You can just replace the pot with what ever you get and see how it works out.
Drop a not after you've done this and how it worked out.
Attached Here is edited cut from simplified circuit of 2340sx, to illustrate what I was talking about. Also I am attaching scan of pots positions, just in case. I was not sure about which exactly pot did you break, as in 2340sx 33K pot is actually Record CAL pot, but it does not fit your description, (there must be some differences betweeen 2340sx and 3340s, but they are very similar machines).
Attachments
Thanks! Assuming the circuits are similar, it appears the effect of a value change from 33K to 25K on the monitor cal pot would be minimal on the other settings. I'm going to find out. The thought of putting an extra resistor in series had occurred to me, as had the significant nuisance that would be, so I figured I'd just charge ahead with replacing the pot with what I can get, and then see if I need to tweak it. Of course, it also depends on what setting is required as to where to put the resistor (which side of the trimmer), which is why it's best to have the right value of trimpot to start with!
Either way, thanks a lot for taking the time to scan the schematics. That's very helpful! We'll know soon enough how it goes... the replacement parts will be delivered today. I ordered a bunch of both values, since they are cheap to avoid more shipping charges if another pot bites the dust.
Also, I did some record adjustments last night and was surprised to see that the rec eq coil didn't seem to affect response very much. Oh, well, the bottom line is that even though it doesn't yet meet factory spec, it sounds great! Seems to have a bump around 100 Hz that is more than +3 dB. I guess that will compensate partially for the room resonances below that!
Cheers,
Otto
Do you have the ability to save individual pages as separate .pdf files, or perhaps as some other type of image file (jpeg or gif)?
Cheers,
Otto
SteveM
New member
That's what I don't know. I'll try it but I had to use someone elses back up drive for my stuff, so I have to get it. I had a back up emergency happen about a month ago. I can probably try it tomorrow. I'll PM you and let you know if I was able to take a page out.
sweetbeats
Reel deep thoughts...
Don't know if this will help or not, but there are a number of Teac and Tascam manuals available for free download here: http://safemanuals.com/
They have the A-3440, no 3340, but there are 4 separate A-3440 downloads which I believe include operations, service and schematics.
They have the A-3440, no 3340, but there are 4 separate A-3440 downloads which I believe include operations, service and schematics.
I installed just the 25K trimpot. A smaller pot, but same footprint for the leads. I was worried when I saw them in the bag. Seems basically the same, which is good news!
I will need to redo things anyway. I'm going to bias by modulation noise, but I need to redo the playback levels first. I'm using a +6 tape, but I forgot that's asking a bit much, so I'm going to set it back to +3 and maybe this time I'll remember it's also a bit much to do the record calibration at reference level on this machine!
Cheers,
Otto
I will need to redo things anyway. I'm going to bias by modulation noise, but I need to redo the playback levels first. I'm using a +6 tape, but I forgot that's asking a bit much, so I'm going to set it back to +3 and maybe this time I'll remember it's also a bit much to do the record calibration at reference level on this machine!
Cheers,
Otto
I ran through the electronics on the Teac again last night and things got better. The machine is now to the point where it can be used. The new trimpot on the source monitor calibration worked best of all four channels! In case anyone needs one of those trimmers, it's just a 25K 6mm carbon trimmer pot, horizontal mount, vertical adjust made by Piher. I got mine from Mouser Electronics.
We were speaking of biasing in the ATR thread. I tried Bill Vermilion's advice last night for the first time I can recall and I did rec bias on my Teac A-3340S by minimizing modulation noise. You can probably still find his article on Google groups somewhere and Howard Sanner has it on his recordist.com/ampex page.
Very quick and easy, done by ear and it does the best possible job of taming annoying bass modulation noise. Also ended up in about the same place I had by using the factory spec procedure.
You just run a test tone in at about 7 Hz, start record, monitor off the tape and adjust (increase) bias until the helicopter noise goes away and things get quiet. If you keep increasing bias, the noise comes back with a change in tone. Just go back to the quietest point. Works like a charm and you don't have to worry about whether to bias at 1K or 10K or 15K and how many dB "over" to go or looking up data sheets on the tape or (in my current case) not being able to remember whether the test reel is SM 911 or SM 468!
Having run through the electronic process a couple of times now on the Teac, it seems to be settling in. I was too lazy to mess with mechanical alignment until the electronics were a bit closer. You may find that if a machine hasn't been used for a while and everything is way off that you kinda need to regard calibration as an iterative process... i.e. you go through it once and you get close and then you go through again and things settle down more.
The Teac is much closer to factory spec, though I discovered off the bat that my old Ampex test tape is a sticky piece of junk, so I used my MRL IEC1 tape instead. Overall system response is close, but there is still a broad peak from 1K to 10K that is bigger than the factory spec of +3dB on a couple of channels.
Of course, the fun part is that the darn thing already sounds great. Once I get the M-23 up and going, I'll go back and do a proper alignment on the Teac where I actually do the mechanical alignment, too. It always takes me a little while to recall how to set up the scope when it's been a while since I've done an alignment.
Cheers,
Otto
We were speaking of biasing in the ATR thread. I tried Bill Vermilion's advice last night for the first time I can recall and I did rec bias on my Teac A-3340S by minimizing modulation noise. You can probably still find his article on Google groups somewhere and Howard Sanner has it on his recordist.com/ampex page.
Very quick and easy, done by ear and it does the best possible job of taming annoying bass modulation noise. Also ended up in about the same place I had by using the factory spec procedure.
You just run a test tone in at about 7 Hz, start record, monitor off the tape and adjust (increase) bias until the helicopter noise goes away and things get quiet. If you keep increasing bias, the noise comes back with a change in tone. Just go back to the quietest point. Works like a charm and you don't have to worry about whether to bias at 1K or 10K or 15K and how many dB "over" to go or looking up data sheets on the tape or (in my current case) not being able to remember whether the test reel is SM 911 or SM 468!
Having run through the electronic process a couple of times now on the Teac, it seems to be settling in. I was too lazy to mess with mechanical alignment until the electronics were a bit closer. You may find that if a machine hasn't been used for a while and everything is way off that you kinda need to regard calibration as an iterative process... i.e. you go through it once and you get close and then you go through again and things settle down more.
The Teac is much closer to factory spec, though I discovered off the bat that my old Ampex test tape is a sticky piece of junk, so I used my MRL IEC1 tape instead. Overall system response is close, but there is still a broad peak from 1K to 10K that is bigger than the factory spec of +3dB on a couple of channels.
Of course, the fun part is that the darn thing already sounds great. Once I get the M-23 up and going, I'll go back and do a proper alignment on the Teac where I actually do the mechanical alignment, too. It always takes me a little while to recall how to set up the scope when it's been a while since I've done an alignment.
Cheers,
Otto