Tascam Porta Two: Sound coming in mono / No left channel

[adogus]

Hi. Recently I bought a used tascam porta two. It should be noted that I'm currently running it on batteries. While testing with my cassettes, I noticed these things:
-While listening from headphones output and remix mode, I can only hear right side, however there is a very quiet signal on the left (could not confirm if it's from the left bus).
-While listening from headphones output on cue mode, sound just comes in mono. (I think it might be how it's supposed to work)
-While listening from line out, strangely right channel comes to both sides, but when I pan it all left, there is a quiet signal on the left side and no sound on right side. This only happens when all channels hard panned to left.
I checked the manual however I could not understand what I'm doing wrong. And if it's a malfunction, i'd like to know if a fix is possible. Appreciate if anyone could help!

 

[SkywaveTDR]

It is hard to tell what is going on but may be a broken solder joint in one or more than one place.
I find it hard to define what part is bad by description of this kind.

 

[BazzBass]

you are asking what could be wrong with a 36 year old machine.......

....probably every third solder joint.

Can you follow schematics, testing for continuity at every joint?

 

[adogus]

I was going to attempt to at least look for broken solder joints on the signal path, but could not find the shematics online. I assume it's in the "service manual". Not sure where to search it.

 

[-mjk-]

If you bother to open it up to fix broken solder joints, you should just res0lder all of them. No schematic needed.

 

[SkywaveTDR]

That would be a lot of soldering with possible mistakes also added in. I do resolder some board but with good light and magnifiers on and I find solder beads from manufacture that were left in. A lot of these wave soldered board are pretty bad but the Porta Studio with all the switches and jack around connectors can add to what is there trouble wise. Good paper manuals used to be from Stereomanuals.com but Risk died last year and I am not sure what will happen to the manual business there. It is a gold mine of manuals bit also a very big job. Maybe this is best handles by tracing the signals with a scope and finding the real problem.

 

[adogus]

Thank you all so much, by looking at the block diagram in the manual, I was able to narrow down the problematic part. VU meters too cant read any signal from left buss, so it's not jack. I'm guessing it's eighter the master fader or amps just before and after the fader. A youtube video gave me the idea to bypass the fader by using jumper wires to test it and as a temporary solution. Is that a good idea?

 

[adogus]

I dissasembled the device, blew the dust off, checked cable connections, checked for broken solders around the area I was suspicious of. Found nothing visibly bad. Reassembled it, and to my suprise it was working! I'm guessing there is a loose contact somewhere so the problem might occur again, but at least I can finally have some fun with it now!

 

[SkywaveTDR]

Well if it is technically sound. Most You tube people do not have a clue they just rummage their way through but I doubt they really fix anything. A Master fader can be ohmed out with a meter so there is no need to jump anything. They can be opened up and checked for cracks- you should see a crack in the back as well if there is one there. One guy had a decayed carbon trace maybe due to some junk like salt crystals that got in there- people do not cover these and treat them poorly and wonder why they break. A carbon trace can be enhanced to some degree by a conductive pe

 

[SkywaveTDR]

Yes the fuzz that is in the deck can also get into the fader and stop them from conducting. Maybe this is what you found. The blowing of dust out usually just puts it into other parts that make it worse so vacuum the deck while brushing with a paint brush is the better way.