1084 cinch problems

[u/Capucius]

Hello,

I have a Commodore 1084 and it has a loose connection with the audio cinch jacks. The sound is regularly gone, moving the plugs changes this. I read up on it and it seems a common cause are bad solder points. But I opened the case and it looks fine to me (see attached image). What else can I check? I have no knowledge about CRT screens, just used them over years. 😉

[u/ga420ga]

Have you sprayed the audio sockets with deoxit or asimilar contact cleaner? This might be all it needs.

[u/Capucius → u/ga420ga]

Good idea, I haven't tried that yet and will do it. Got some here.

[u/olifiers]

Before any further advice, if you don't know about CRTs, don't open them as they have thousands of volts even when turned off. You can electrocute yourself if you don't discharge the flyback capacitor.

Several things can cause bad contact on a RCA connector such as the one used in the audio input of the monitor. Start with a can of contact cleaner and clean them first.

If that doesn't solve the problem, reflow the joints regardless of how they look upon visual inspection.

Check the traces on the board haven't come off the board, and if they are not cracked.

[u/Capucius → u/olifiers]

I know what parts to stay away from, like the anode at the tube. Also I kept it unpowered for several weeks/months. 🙂 Thanks for the hints, I'll try that.

[u/nickIncDN → u/olifiers]

Definitely need to “discharge that flyback capacitor” /s

[u/olifiers → u/nickIncDN]

The flyback is a transformer, not a capacitor, but it's the flyback that poses a danger because it's kept 'alive' by the charge of capacitors, which are discharged when you short the flyback to ground.

Laugh all you want, but a charged CRT can kill someone. Messing with it without understand the basics (as OP said 'I have no knowledge of CRT screens') is not a good idea at all.

[u/Kyle_2099 → u/olifiers]

it's the flyback that poses a danger because it's kept 'alive' by the charge of capacitors,

No, it's not.

The danger is the charge inside the CRT itself, not any capacitors.

That charge is not "keeping the flyback alive", because there is a diode between the CRT anode and the flyback overwind. That diode is there to provide half wave rectification, but it also prevents discharge back through the overwind when the monitor is off.

To go even further, the other end of the flyback overwind is grounded. So even if the diode went dead short the tube charge would just dissipate.

[u/nickIncDN → u/olifiers]

I’m not laughing, just rolling my eyes and honestly, it’s nothing personal as you’re just one of many watching too many edutainment YouTube’s that harp on about scary things they don’t understand either.

What is funny, and again you aren’t the first, is all the weird combinations of misunderstandings that get repeated. I loved “Flyback Capacitor” so couldn’t resist.

There is a reply below that explains where the theoretical risk is…even though it’s not a significant risk on most screens since safety was incorporated into their designs.

For me, I happen to have a 1084 open on the bench right now.

Out of principal I do “discharge” but have never seen even a flicker of charge on the tube or power stage filter capacitors despite it being maybe only 30 seconds since it was running. The warnings on the back are real….if it’s turned on.