grundig: 6099; Konzertgerät

 

Greetings

A while back I started to restore a Grundig 6099 that was in pretty deplorable state when I got it. Not only had it been stored in a damp environment for a long time but it also had physical damage: cracked cabinet including plastic surround etc. Anyway I'm now at the point where the cabinet has been restored (glued back together, refinished etc.), the chassis has been recapped etc. and the radio is working again, on FM and AM, so I'm now at the point where I have to iron out the remaining wrinkles.

One of the problems I'm dealing with is FM tuning range. It should be from 88 to 100 Mhz but presently the tuning range is from 80 to 92 Mhz, albeit that stations in that range come in loud and clear. My conclusion would be that the oscillator frequency is off, correct? I know that there are adjustable coils on the FM head but my experience with other radios has been that the range of adjustment using those normally is < 5 Mhz, and I'm off 8 Mhz or so.

My question is: what components control the FM oscillator frequency and what should I be checking? I do have the schematics but I guess I'm not experienced enough to really tell what the oscillator's main components are.

Another problem is with the amplifier section. Sound is loud and clear without any distortion for 30 minutes or so, regardless of volume and then there will be a series of loud cracks and plops for a minute or so, followed by another period with it playing perfectly. It does this both when playing FM stations and also when I have an iPod hooked up to the TA input, which is why I believe the problem is in the amp section. What are likely causes for this? Right now I'm cleaning all tube socket contacts - any other suggestions?

Lastly, what is the best way to temporarily disable the automatic tuning adjust? It's a great feature for normal use but it's annoying when trying to troubleshoot the radio.

Best regards,

Ton Regeling

 

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Hello all,

A follow up on my previous message: I found what caused the cracks and plops. It was a bad ECC82. I found it by gently tapping each tube with a pen with the radio playing - and when touching the ECC82 there were lots of cracks and plops. Replacing the tube cured the problem.

I also found the problem with the tuning range being very far off. The wire that pulls the core through the one of the chokes (coils) on the FM head got itself tangled up in one of the springs on the metal bar that pulls the core back and forth. Untangling the wire and cleaning the choke and core (it didn't slide freely) solved that problem.

The only problems that remain are that the entire mechanism for the FM preselect buttons is badly rusted, so the bar that pulls the cores through the chokes in the FM head doesn't move freely, so you have to help it when searching for radio stations. Any ideas here are greatly appreciated. The other problem is that the plastic pinion gears that drive the dial indicators are worn to the point that they no longer catch, making the dial indicators useless. If anyone has these, I'm very interested.

Otherwise this radio now plays great, with a fantastic sound quality, despite the rusty speaker frames and radio chassis.

Best regards,

Ton Regeling

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