Interesting Problem Repairing a Tandberg 9200XD

[cutter]

Hello All
This is my first post to this forum (new Member) and I'm hoping someone might have some insight into a solution for my problem.
I've been repiring a Tandberg 9200XD (4-Track) and after fixing the main issues (bad power switch, Stuck Pinch Roller Pivot arm, Cleaning) I started testing playback and recording. Playback was fine and clear but when I tried recording I hit a snag. There seems to be some problem with the right channel both line in and mic in. When recording stereo there's no movement on the right meter and nothing recorded on the right channel. Just to check the record head I unplugged the right line in and depressed only the right record button. in this setup the right channel recorded just fine. I've been checking the schematics and my best guess is there may be something wrong with the A2 card that handles the input amplification.
I'm hoping there's someone on this forum who might either have some experience with this problem or might be able to refer me to someone.
Thanks in advance

[jdurbin1]

Have you been through the record select, source select, and Sound on Sound switches, the level controls, & any board-to-board connections to deoxidize them? Also, I assume Sound on Sound is switched off for your test...

John

[cutter]

Hi, yes the sound-on-sound was off for the test. I haven't done the deoxit yet (ran out of it Monday) so I'll pick some up tomorrow and give it a try. Hope that's all that's needed*hope*
Thanks

[jdurbin1]

Cool, let us know if that helped...

Do you have the service manual, if it requires more digging into the circuits? I am pretty sure I have the original for that somewhere, although I may not have scanned it yet. LMK once you get the deox service done.

John

[cutter]

Well, unfortunately the Deoxit didn't fix the problem *frown*
I cleaned all the contacts for the A2 board as well as all the input connectors on the main board that connect the Line In and Mic in feeds to the A2. Oh well, looks like I'll start testing the circuits on the A2 to see if anything is faulty.
John, I do have the schematics for the 9200xd, I had downloaded them before I bought it but thanks for the offer.

[cutter]

Ok, after many days tracing circuit diagrams and testing the various circuitboards, I've found no obvious problems. The trace from the right line-in all the way to the input pin for the A2 card has good connection, the A2 card input through to the output for the right line-in seems fine as well, and the circuit trace from the A2 card to the A4 ( Dolby encode) has good connection.
During the testing I decided to switch to headphones to try and see if there's any kind of signal coming through and there is! with only the right line-in connected there is an incredibly faint signal getting through and it's only detectable when the line-in slider is all the way up and the right output slider is all the way up. So now it's a matter of trying to find out why the right channels are doing this. Any one have any thoughts?

[Nakdoc]

Tandberg typically metered AFTER the Dolby encode process, so you've narrowed it down to the record Dolby circuit. The faint sound you hear is crosstalk. Look for an open coupling capacitor.

[cutter]

Well, I took your advice and started testing the capacitors. There was a weak one on the A2 board so I replaced that but it didn't change the output. I switched the 2 Dolby record cards to see if it affected either channel but there was no difference. I don't think the problem is in the Dolby cards as mono record (which sums left and right channels) does allow me to record on the right channel with excellent results. I still think the problem lies in the A2 as this is the input amplifier and both the right line-in and right mic-in are affected.

[cutter]

Well, I think I'm going to stop here with the 9200XD. I've spent a lot of hours tracing and testing and occasionaly replacing (capacitors) all with no avail. There's definately something wrong some with the right channel somewhere along the line. My last attempt was a capacitor on the right Dolby card and I had my fingers crossed but still no change. With the left and right record channels active I can record both channels if I push the sliders to the top and push the mixer into clipping so that there's enough signal getting through. This will put enough signal through the right channel so that if I have only the right channel connected to the inputs it will produce enough signal. Of course it sounds crappy but there's obviously some signal being passed, just not all the signal.
Now on the playback side it sounds wonderfull. I might use this in the house rather than in the garage studio as I was planning. I think for 99cents it's one amazing play back deck for pre-recorded tapes.
I did just pick up a Tascam 22-2 for the studio (no problems listed with this-yet) So I'll put the Tandberg back together and use it as is.