Pioneer CT-F950 issues

[MAG_1944]

I've recently purchased my first vintage cassette deck, a 1979 pioneer CT-F950.
Having set it up and run a few tapes, there are a couple of things I have noticed and I'd like a little bit of advice on:

Before I ran it, I cleaned the head, roller and capstans with some IPA.

• There is a pop noise every 6-9 seconds on both channels. The VU meter will jump up considerably when I have it set to peak hold. I've used 3 different cassettes which I've checked in another player so I think we could rule the tapes themselves out. Is there anything I can do to attempt to rectify this?
• The drive mechanism also seems to be a bit noisy, while playing and fast forwarding there is a "cher-chunk" sound every 3-4 seconds, it's not really loud but it is noticeable during quieter parts of the song. When rewinding, this sound isn't as loud or noticeable. Obviously a tape deck isn't going to be silent running but how much noise is to be expected and should it be more of a consistent whirring rather than fading in and out?

I did take the front plane and rear cover off to look at the belts and they aren't showing any signs of cracking or leaving residue on the flywheel or rollers. Could this be a case of old dried lubricant in the bearings?

As a cassette deck novice, any advice would be greatly appreciated.

 

[SoundGammon]

I have a CT-950 that had some issues and I was able to rob a few parts from a CT-900. Try this: put in a tape and hit play and then pause. Also try putting it into record mode with no signal coming in.Is the popping noise still there? It sounds to me it might need some filter caps in the power supply since both channels do it. As for the "cher-chunk" noise, it might be a bad rubber tire on the wheel that turns the reel spools. How does it work in fast forward & reverse?

 

[MAG_1944]

So having put the tape in and hit pause, I can't hear the pop. But having then put a blank tape in and hit record with 0 input and then listened back, the pop is present.
The "cher-chunk" noise is there while fast forwarding, but it's more of a continuous thrumming noise due to the increased speed. However while rewinding, the noise isn't present which makes me think it's something on that capstan only.

 

[koltrast]

The ”Ker-chunk” you will sadly have to live with. The deck`s spindle is of a smaller dimension relative to the cassette’s hub (obviously) and therefore the weight of the pack on the supply side will drop with a Ker-chunk as it turns. This will get progressively less as the tape transfers to the take-up side due to the pack weighing less.
The problem doesn’t exist on the take-up side as there is take up torque. On rewind there is drive on that side and thus no drop, but maybe on the right, take up side. Does this make sense?
This is not an issue specifically on Pioneers, but is a lot louder on the CTF models as the tape is on the outside of the deck, i.e. no sound dampening.

 

[koltrast]

I would add the popping is either a grounding problem or bad caps.

 

[SoundGammon]

Just remembered that this is a closed loop dual capstan design. If the unit has sat for a long time there's a good chance the belt has a "dent" where it sat around the motor pulley from not moving! I've had a belt do this on my Marantz 6200 turntable and I could hear a "thunk" every time the dent went around the motor pulley! I took off the belt and sure enough you could see the "dent" in it! Now I remove the belts from my turntables if I don't plan to use them for awhile. See if putting on a new belt helps! I think you can get them on E-Bay!

 

[MAG_1944]

Thanks for all the input, I checked the deck without a tape in it and the clunk is still there so the weight of the tape isn't the only cause.
If I'm looking to replace the belts, are there more reputable sellers to use on eBay or anyone on here who I'd be able to order them from?
For checking the grounding issue; is that simply a case of getting the service manual out and checking all the connections which route to ground? Should this be a visual check or is there anything I need to use a multi meter on?
Thanks