Tascam 32 Fix found.

evm1024

evm1024

New member
My Tascam 32 did not playback on the right channel in reproducer or sync mode. Sync would work sometimes. record was OK. I've been looking for a schematic before digging into it too deeply.

The connectors on the "motherboard" for sync was sensitive to touch. Twiste it just right and sync would work. (Execelent I thought!)

Inspection showed that BOTH the right channel sync and reproduce connector pins were cold soldered. A quick touch with my soldering iron and some silver solder and Poof (Orange smoke dissapates) the channel was solid.

I still need a schematic...and the headphone amp has a lot of hiss.

Regards
 
evm1024 said:
I still need a schematic...and the headphone amp has a lot of hiss.
Click to expand...
There was another thread here about the hiss, and a 32 I borrowed last week was very hissy also. I'll wait until mine arrives from Auckland before saying for sure, but I'm guessing that its just a very noisy headphone amp, i.e. a design fault.
 
arjoll said:
There was another thread here about the hiss, and a 32 I borrowed last week was very hissy also. I'll wait until mine arrives from Auckland before saying for sure, but I'm guessing that its just a very noisy headphone amp, i.e. a design fault.
Click to expand...
Mine is virtually unusable. It can't have left the factory in that condition.
 
jpmorris said:
Mine is virtually unusable. It can't have left the factory in that condition.
Click to expand...
I would call the one I borrowed unusable, I know its history (sold it brand new to the local community radio station when I had an account with the NZ Teac agents about 13 years ago) and it has had very little use.

When I copied some stuff off last week I monitored from the direct out on the US122, the headphone out was unusable. Thats two, plus the two others on an earlier thread, so I'm guessing it wasn't really designed to be used for serious monitoring. Would be interested if you can work out a fix though - I'll be wanting to modify mine when it finally turns up...
 
evm1024 said:
I still need a schematic...and the headphone amp has a lot of hiss.
Regards
Click to expand...

The schematics are big, they unfold like maps and would be difficult to scan in. I can probably do just the headphone amp if you like, though.
 
jpmorris said:
The schematics are big, they unfold like maps and would be difficult to scan in. I can probably do just the headphone amp if you like, though.
Click to expand...

Thanks, Please do the headphone amp.

I'm thinking that I will make it a project to discover the source of this hiss and a cure for it.

It could be aged components or the monolithic headphone amp. In any case it should not be there.

It appears that the modular boards in the 32 are intended to fit the 34 aqnd 38. So I presume that this same headphone amp is in them as well. How widespread is the noise problem?

Regards
 
A Reel Person said:
but the 34B does.;)
Click to expand...

OF course. THe 32's headphone amp board also has the 2 micraphone preamps on it so it would not be interchangable.

What mods do we know avout for the 32?

Regards
 
evm1024 said:
Thanks, Please do the headphone amp.

I'm thinking that I will make it a project to discover the source of this hiss and a cure for it.
Click to expand...
http://www.jpmorris.force9.co.uk/music/32_headphones.gif
http://www.jpmorris.force9.co.uk/music/32_headphones_pcb2.gif

..I make no guarantees as to how long I'll keep them there, so if anyone else wants to grab them, do so now!

What doesn't show on the scan is that R309 and R409 are flagged as being 'safety critical'.. this must be one badass headphone amplifier.
 
jpmorris said:
http://www.jpmorris.force9.co.uk/music/32_headphones.gif
http://www.jpmorris.force9.co.uk/music/32_headphones_pcb2.gif

..I make no guarantees as to how long I'll keep them there, so if anyone else wants to grab them, do so now!

What doesn't show on the scan is that R309 and R409 are flagged as being 'safety critical'.. this must be one badass headphone amplifier.
Click to expand...


Hi,

I just bought my own manual/schematics off eBay.

The gif do not show the TA7230P (U302) which is a 4 watt power amp. This is the actual headphone driver amp.

R309 and R409 are on the plus and minus supply of and limit current to the opamp U301.

This is enough to get me going on locating the source of the noise. It will be nice to have the schematics when they arrive.

Regards
 
evm1024 said:
Hi,

I just bought my own manual/schematics off eBay.

The gif do not show the TA7230P (U302) which is a 4 watt power amp. This is the actual headphone driver amp.
Regards
Click to expand...
Sorry, since they were on opposite sides and not connected, I assumed they were separate. I've replaced the schematic gif with one containing the entire card.

Here is the PCB layout for the right-hand-side of the card:
http://www.jpmorris.force9.co.uk/music/32_headphones_pcb3.gif
 
Nice scans!

Bad transistors are likely culprits for hissy output, Q301 and Q401.

-Tim :)
 
Beck said:
Nice scans!

Bad transistors are likely culprits for hissy output, Q301 and Q401.

-Tim :)
Click to expand...

Hi Tim,

I would say that the U301 is the mic preamp (which shares the same board) and that the FETs Q301/401 are the -20 dB attinuator switches. You can see that they change the feedback loop.

The TA7230P has 48 dB gain so it should not need another gain stage.

Regards
 
Headphone amp as suspected.

Yup, The fets are in the mic preamp. Here is a photo of the board. I'll update as I have more information (a solution?)

Regards
 
And the photo....

evm1024 said:
Yup, The fets are in the mic preamp. Here is a photo of the board. I'll update as I have more information (a solution?)

Regards
Click to expand...

OK the image was too big...
 

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just a thought...

would this make sense?.... if the amp is 'noisy' , then to bypass headphone amp, wire it to headphone output, and then use an external headphone amp, like this for example: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7338596975 (i saw them on e-bay going as cheap as 15 bucks used)
I have one of these lil Rolls Headphone amps...and it's just fine.
....
well, my point is, this maybe easier way to get around the problem if you really need to monitor directly from the machine.

You also can add a two position rotary (or push button) switch for the headphone jack: one position is WF - "water fall" (original internal amp), the other one: SD - "silent death" (direct bypass out to be used with external headphone amp). Well, I don't see any space for a switch thou.... ;)
 
WF vs SD

Dr ZEE said:
just a thought...

would this make sense?.... if the amp is 'noisy' , then to bypass headphone amp, wire it to headphone output, and then use an external headphone amp, like this for example: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7338596975 (i saw them on e-bay going as cheap as 15 bucks used)
I have one of these lil Rolls Headphone amps...and it's just fine.
....
well, my point is, this maybe easier way to get around the problem if you really need to monitor directly from the machine.

You also can add a two position rotary (or push button) switch for the headphone jack: one position is WF - "water fall" (original internal amp), the other one: SD - "silent death" (direct bypass out to be used with external headphone amp). Well, I don't see any space for a switch thou.... ;)
Click to expand...

If it is a component fault I'll just replace it. If the power amp is the fault (design fault) I'll just replace the whole amp.

THis decks prime use is onsite recording of classical pipe organ and the headphone amp should be quiet....Plus it is my nature.

Regards
 
evm1024 said:
Yup, The fets are in the mic preamp. Here is a photo of the board. I'll update as I have more information (a solution?)

Regards
Click to expand...

Ah, I believe you are correct. That will teach me to just glance at the parts list. I couldn’t see how they tied in to the mother PCB, so I grabbed my service manual for the TEAC 32-2B, which is a slightly different animal.

It uses an HW11122W for all monitor amps; 1/6 for output, headphone and meter for left and right channels. I have found quite a few hissy transistors, mostly in mixer pres though.

Well, at least the headphone circuit on the 32 isn’t too complex, so you could replace everything if need be fairly painlessly. Perhaps dried out capacitors? However if the hiss is in both R&L channels maybe the amp IC. I’m interested to see what you find.

-Tim :)
 
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