Pioneer CTF9191

[Pure_Brew]

Hi,
I have this old tape deck and after changing a couple belts, it seems to work fine, for awhile.

What happens is that the sound is clear for about a minute or so, then a low level hum appears on the right channel and continues to grow into a loud hum/chipping sound. This is audible from the output to an amplifier or plugged in by itself and monitored via headphones. The right hand meter pretty much tacks out, bouncing with some of the "chipping" sound.

If I shut it down for a minute or so, the same thing happens - clear then growing noise in the right channel.

Any Idea what this is from and what I might be able to do about it would be awesome.

Thanks!

[Mooly]

Very hard to diagnose something like this but we can try...

Did it work OK before the belt change ?

Does the hum continue if you just press pause ?

Does it have the long mechanical "record/play" switches on the main PCB somewhere. These have many pins (guessing anywhere between 20 to 50) and are acted on by the record key... usually two, one for each channel... notorious in all makes and models for strange audio problems. Give 'em a squirt of WD40 and work to and fro by hand.

[Pure_Brew]

Heeeey it my main man Mooly! How've you been?

Doesn't matter what I do. The hum comes back always after time and doesn't go away until the unit is off for a while. I can play, pause, record and it comes back. It was humming a long time ago before I changed the belts. I don't think it hums just sitting there turned on. I'll have to dig it out of the closet again. The last time I used it started chirping like a siren every second while I was recording and the audio in that channel was almost completely gone ( music audio that is).

Would it be a waste to recap?

[Mooly]

Originally Posted by Pure_Brew

Heeeey it my main man Mooly! How've you been?..............Would it be a waste to recap?

I'm good thanks

Have you actually tried moving the record/play switches while it's on to see if it alters the fault... these were such a common problem 20+ yrs back and I'm guessing something of this age uses them.

Recap... not on the off chance of fixing it. You need to be sure.

Is the hum a pure hum or is it a buzz/noise ? Anything PSU related would show in both channels I would imagine...

[stratus46]

Originally Posted by Pure_Brew

Heeeey it my main man Mooly! How've you been?

Doesn't matter what I do. The hum comes back always after time and doesn't go away until the unit is off for a while. I can play, pause, record and it comes back. It was humming a long time ago before I changed the belts. I don't think it hums just sitting there turned on. I'll have to dig it out of the closet again. The last time I used it started chirping like a siren every second while I was recording and the audio in that channel was almost completely gone ( music audio that is).

Would it be a waste to recap?

Probably not a waste as it's the right vintage but it would be more productive to probe it with a scope if you have one. Electrolytic caps typically improve ESR as they warm up and get worse when cold. You can 'shotgun' the caps and as long as you're careful it should be good. I find it 'entertaining' to probe them with an ESR meter. When working on 25 yr old Sony broadcast gear I find that certain values in a given machine tend to be bad while others are OK. Other machines of the same model usually have similar failures.

G²

[steph_tsf]

Schematic here :
http://akdatabase.org/AKview/albums/...110%20Volt.pdf

So over time you get more and more hum on the right channel, & apart from this everything sounds right.

- is there a difference Dolby ON vs. Dolby OFF ?
- what's happening if you gently move the record-play wires with your finger, while in play mode (bad solder joint somewhere in the record-play wires) ?
- have you tried cleaning the the record-play multiswitch (S2) ?
- have you tried cleaning the the normal/chrome switch (S3) ?
- have you tried changing the input capacitor of the right play amplifier (C202) ?

Regards,
Steph

[Pure_Brew]

Thanks everyone for help here! I'm going to go ahead and clean this all up this week as all of the controls are really cruddy. The Dolby noise, input levels, pause switch and EQ are noisy when moved or touched, and appear bad contact. The popping/crackling made by the switches seems pretty common and does not appear to effect the growing hum, only a cool- down affects this and makes it go away temporarily.

Thanks steph for the schematic!

Originally Posted by Mooly

Is the hum a pure hum or is it a buzz/noise ? Anything PSU related would show in both channels I would imagine...

Well, the hum starts off pure and stays pure ( only right channel) until it peaks out the meter at loudest volume. Then it's pandemonium, making sounds like a "circuit bent" Speak and Spell, like high pitched squeals that have some changing oscillations, sometimes every second, sometimes much faster. And sometimes crackling - loudly.

Going forward, i'm going to have to grab an ESR meter. I'd like a combo DMM as I need to replace mine. Any reasonably priced recommendations would be helpful.

Thanks.

[Pure_Brew]

good news / bad news...

I removed the front panel and cleaned all the controls & switches. It's been like night and day. I'm able to play back without much incident. Seems that the previous issue is pretty much gone and I've been running this for hours. I've had an occasional light hum or hiss in the right channel but I've heard none of it in the past couple hours.

no capacitor testing, yet...

Recording is another issue though. The left channel wants to fade out or not come on at all when recording unless I fool with the power switch, turning the unit off then back on. Theres actually a reduction across both channels too when the left fades (sweep meter drops silent). Switching off/on starts some left channel crackling at first then it clears up. Sometimes I can get the recording going well for a long after doing this a few times. I've been monitoring through headphones during recording and I don't get drop outs when playing back (unless its a recording I made with the left channel dropping out of course.)

I cleaned the heads, roller and capstan to no effect (but wow dirty).

Thing that sucks now is that the power switch shattered internally, so I soldered a bar across the terminals temporarily and have to switch it at the wall (BUMMER!). When I cleaned it I must have blown out any lubricant it had at all, as it got really stiff after cleaning. Will be hard to get it replaced and most likely not worth it.

[Mooly]

Pity about the switch... it's probably not unique if you looked for scrap equipment of that vintage.

As to the crackling/fading. Until the R/P switching has been proved OK it would still be under suspicion. Fading that improves on power on/off. Could be mechanical like a back tension issue or a tape path issue. Maybe the tape wanders across the tape path.

[Pure_Brew]

Well its an ancient blank Realistic C-60 tape that has recording on it, and has been sitting in the machine for years as well. I'll try a couple tapes later on.

Q: Is it safe to use WD-40 on these types of switches? FYI the first picture is the power switch (broken now)

https://picasaweb.google.com/lh/phot...eat=directlink
https://picasaweb.google.com/lh/phot...eat=directlink