Cap replacement/ discharging CRTs

[iainjh]

Hi

a couple of questions I'd like to put out there re capacitors/batteries replacement if I may. I read a post about replacing caps in a mac se/30, and of course was reminded about discharging the CRT.

next thought is what else is it sensible to replace caps on -

1. my vectrex - anyone know what caps are at risk / need replacing in that? (I'll get the CRT discharged on that too)

2. I've also got an apple 2e and an atari 800 I want to look after. anyone got any info /experience of replacing caps in those as my searches arent so fruitful.

I've also got a 1081 monitor with a broken power switch. do I need to discharge that crt too before I replace?


If my old man was still about I'd have him do it as he was a computer / tv engineer; wish I'd listened a bit more. The last time I discharged a crt was when I was about 12 and I'm... well, far too scared to do it myself now haha

ta all for any advice and info or weblinks!

Iain

 

[FOL]

Hi

a couple of questions I'd like to put out there re capacitors/batteries replacement if I may. I read a post about replacing caps in a mac se/30, and of course was reminded about discharging the CRT.

next thought is what else is it sensible to replace caps on -

1. my vectrex - anyone know what caps are at risk / need replacing in that? (I'll get the CRT discharged on that too)

2. I've also got an apple 2e and an atari 800 I want to look after. anyone got any info /experience of replacing caps in those as my searches arent so fruitful.

I've also got a 1081 monitor with a broken power switch. do I need to discharge that crt too before I replace?


If my old man was still about I'd have him do it as he was a computer / tv engineer; wish I'd listened a bit more. The last time I discharged a crt was when I was about 12 and I'm... well, far too scared to do it myself now haha

ta all for any advice and info or weblinks!

Iain

You should discharge everything before working on it.

i.e. PSU Smoothing caps (these like to hold charge if not power down correctly) and the Anode Cap (These one is'nt always needed, but best to be safe than sorry).

 

[zaxon]

If your hardware was disconnected from power supply from 1-2 weeks or longer discharge capacitors or CRT is not important becouse capacitors discharging self. But on crt tube anode cap is 20 000 - 28 000 volts, so if you don't have experience be careful.

But important is also discharge you when you working with electronic board but is simply before you start touch water pipe .
I living in Northolt, so not very far i have equipment so can help you.Free of charge of course.

 

[dabone]

I'm a little old school, over the years I've collected and repaired Arcade games and that includes doing alot of monitor repair over the years.
Alot of people say you should have a large resistor in the line while discharging a tube, but I find that taking a section of heavy wire, (Good speaker wire, or one section of a ac wire), stripping enough to wrap around the base of you screwdriver 5 or 6 times, followed by some electrical tape, then strip off a section on the other end.

I always use a medium size flat blade with about a 8in shaft and a good insulated handle.

take the end of the wire and wrap it a few times around the frame, and the ease the tip of the screwdriver under the anode, you will hear a snap, and then you may remove the anode. I prefer to do this a couple of times before I remove it. Also remember to discharge the tube before you put the anode back on, because it will build up a charge just sitting there. (Won't kill you, but can smart a little).

I've fixed alot of monitors and tvs over the years and using this method I've never had any problems. (And yes I've used this on the early macs also.)


Later,
dabone

 

[iainjh]

thanks guys

Zaxon, I'll pm you if you are ok with me bringing the kit over. I'll have the screws out so we're ready to go. Thats ace, thanks again

ta again!

anyone got info about capacitors and batteries for all (except the mac I have that info) that'd be gratefully received

 

[Justin]

i use a cat in a bowl of water:nod:

 

[iainjh]

btw zaxon, re the mac - you got this, resistor included?

http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html#DischargeCRT


no cats expected

 

[rkauer]

Reading the upper site, the flyback on Mac models over 512k RAM already have a discharge resistor built-in.

No need to discharge the tube.

 

[zaxon]

Hmm, no but i have 15 years experience and better tools

 

[iainjh]

as I said before then, ace

 

[bebek]

First time I want to discharge CRT (was maybe 15) I have used my brand new multimeter. I set it to current 20AMP and one probe to ground, one to anode, I thought it would be nice to measure the current too :nuts: and bang - new battery was discharged in a blink and multimeter was never the same again. Experience costs ...

 

[FOL]

Reading the upper site, the flyback on Mac models over 512k RAM already have a discharge resistor built-in.

No need to discharge the tube.

Even though, still better to be safe than sorry, .

---------- Post added at 15:19 ---------- Previous post was at 15:17 ----------

First time I want to discharge CRT (was maybe 15) I have used my brand new multimeter. I set it to current 20AMP and one probe to ground, one to anode, I thought it would be nice to measure the current too :nuts: and bang - new battery was discharged in a blink and multimeter was never the same again. Experience costs ...

Not saying what I was taught to use for discharging.
Lets just say, we ended up making a CRT discharger, using resistors and capacitors.