UHER 4200 Report Stereo - Channel 2 muffled

[DannyGrant]

Hello!

Just got a UHER 4200 report, which is working perfectly apart from the output of channel 2 being rolled off quite a bit. The output gain is more or less the same on both but channel 2 sounds like there’s a low pass filter on it. This is present both on new recordings and pre recorded tapes. I’m using the 5 pin din radio input/output.

The heads had been cleaned by the seller but I cleaned them again to be sure. This is my first machine and if it’s an electrical issue I’ll need to take it to be serviced. Just trying to diagnose the issue first and see if there’s anything I can try myself.

Many thanks

[TIMTAPE]

Hi Danny and welcome.

Does your model have small felt pads on a brass strip which push the tape onto the two heads when play is engaged? If so these may need replacing.
Later models used a plastic u shaped piece to hold the tape against the play head from either side of the head.

Many heads arent cleaned properly because it's hard to see the head face to know when it has been fully cleaned.

With these machines access to the head can be cramped but if you remove the relevent covers you may be able to carefully get a dental type inspection mirror in and inspect the head's face under good strong light and magnification if needed. If yours has the felt pads on the brass strip be careful not to damage those parts.

If certain tapes have been played on it, there could be some quite hard to remove muck on the head faces. Dont rush the cleaning.

Tell us how you go with it.

All the best,

Tim.

PS is yours the Report or the Report Monitor?

[DannyGrant]

Hi Tim, thank you for your reply!

It is the report model with 2 heads. I does have the felt pads you mentioned, I've attached a couple of images. If these do need replaced I guess I'd need to just cut some felt to size?

I'll have another look at the heads too.

Cheers!

[TIMTAPE]

Hi Danny,

I'm a tech in the business, so doing this sort of work on tape machines regularly.

I replaced the felts on two Reports recently. Tricky job but I was able to carefully remove the entire brass strip from the machine with a pair of fine tweezers. The brass strip sits by friction in the slots (I think it's keyed into the right guide so needs to be first lifted clear of the left slot and then slipped leftwards) so replacing the felts was much easier though still fiddly. The brass strip sits by friction in the grooves of the plastic guides.

If you attempt it, make sure the felt is of the same thickness.

Cheers Tim.

[DannyGrant]

Hey Tim!

Thanks again for your advice. I managed to change the pressure pads, and I have cleaned the heads thoroughly. The problem is still present unfortunately. It is relatively subtle, the 2nd channel rolling off from around 8K. Anything else you think it could be?

Best

Danny

[Aub]

Is there any way to swap the connections from the heads, so to determine if the fault is head related or amplifier related?

Cheers

Aub

[TIMTAPE]

Originally Posted by DannyGrant

Hey Tim!

Thanks again for your advice. I managed to change the pressure pads, and I have cleaned the heads thoroughly. The problem is still present unfortunately. It is relatively subtle, the 2nd channel rolling off from around 8K. Anything else you think it could be?

Best

Danny

. Well done. Did replacing the pads help at all? Yes a rolloff above 8k could be a lot worse. I assume you mean at 7.5 IPS. As said, swapping head leads can confirm problem is the head. If rolloff stays with the head's right track, I would physically remove the head to get a really good look at the face under strong light and magnification. Pressure pads are not kind to heads and can create nasty divets which lead to poor tape to head gap contact. Carefully remove the screws either side of the head but don't touch the small height adjuster screws front and back. This assumes the problem occurs in playback, not just record. Muffled recordings can commonly be caused by wrong record bias.