I have a cab that has hissing under the anode cap,monitor works fine with a lovely picture,I suppose I should just discharge and clean the anode cup?,do I need to apply grease to try and cure this?,also ithe tube is in a chipboard frame,not metal,so is it ok to just clip to one of the tube frame bolts to discharge?
Hissing under anode cap
- Thread starter stevebm1
- Start date
A common issue with CRT usually due to slight ingress of damp or poor fitting anode lead terminal
Grease is NOT recommended it makes the cap difficult to grip can trap future moisture and spread to other parts of the cabinet once it gets on your hands … a disaster preventable by keeping the tube clean and dry
Usually such hissing subsides as tube temperature build up try blowing it for 5 minutes with a hair drier round the cup and lopt area of the chassis… but if it’s in a cold room it can attract small amount of condensation as it cools at power down.
Discharging the tube at anode removal is always recommended but few people say discharge it again prior to refitting the anode cap if it’s only been off a short time as a static charge can reappear ? Not often but not desired while cleaning the area or squeezing the spring terminal back into the tube recess…
I am sure one of the monitor experts on here may suggest a permanent cure for persistent hissing cases? Like changing the lopt for one with a better fitting lead seal maybe …. If it can’t be heard while playing and picture is good and clear it may be better left to see if it sorts itself after a hairdrier warm up? … I never had any belief in slonking any additional substances to the area … some stiff old cups warp and allow damp air under and other soft ones do perish . Also if they have ever tracked high voltage in the past a permanent scar of that will be present in the underside of the rubber encouraging it to arc a bit? Just my opinion !! Not gospel!
The cup can be swapped . Desolder the end spring terminals slide it off and fit a new or better one . Re-solder the spring end to the lead conductor wire careful not to leave a spike on any solder at the joint as it could still arc to the glass at that point?
Grease is NOT recommended it makes the cap difficult to grip can trap future moisture and spread to other parts of the cabinet once it gets on your hands … a disaster preventable by keeping the tube clean and dry
Usually such hissing subsides as tube temperature build up try blowing it for 5 minutes with a hair drier round the cup and lopt area of the chassis… but if it’s in a cold room it can attract small amount of condensation as it cools at power down.
Discharging the tube at anode removal is always recommended but few people say discharge it again prior to refitting the anode cap if it’s only been off a short time as a static charge can reappear ? Not often but not desired while cleaning the area or squeezing the spring terminal back into the tube recess…
I am sure one of the monitor experts on here may suggest a permanent cure for persistent hissing cases? Like changing the lopt for one with a better fitting lead seal maybe …. If it can’t be heard while playing and picture is good and clear it may be better left to see if it sorts itself after a hairdrier warm up? … I never had any belief in slonking any additional substances to the area … some stiff old cups warp and allow damp air under and other soft ones do perish . Also if they have ever tracked high voltage in the past a permanent scar of that will be present in the underside of the rubber encouraging it to arc a bit? Just my opinion !! Not gospel!
The cup can be swapped . Desolder the end spring terminals slide it off and fit a new or better one . Re-solder the spring end to the lead conductor wire careful not to leave a spike on any solder at the joint as it could still arc to the glass at that point?
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the cab,is in the house and has been for years,so it's always been at room temperature,,the chassis was serviced by gunblade years ago and had a new lopt fitted at the time,so I doubt it's the actual lopt,I guess I just need to pluck up the courage to dishcharge it,and re-seat the anode cap
I always discharge again before refitting the cap. I know some say it's pointless, but I have seen a small spark sometimes when doing it. This is usually when the tube has been disconnected for some time, I think.
John Bennett
Senior Member
The 34" Polo's I've been trying to repair self-discharge in less than a minute (verified by HV probe) and don't charge up to anything of any significance when left indefinitely, so it must be rather tube/chassis specific whether you'll get tazered or not.
Personally I'm more for waiting a bit of time and using rubber gloves than short-circuiting things with bits of wire. But I suppose you don't know that length of time or every CRT.
Personally I'm more for waiting a bit of time and using rubber gloves than short-circuiting things with bits of wire. But I suppose you don't know that length of time or every CRT.
Its an mtc9000 chassis in this cab,which ones should I check,some appear to have already been replaced
If they've already been replaced then they're likely still ok, but i'd check C36 and C40 just to make sure.
Basically what they said. Make sure the tube is clean and dry. Don't smoke in the vicinity - the nicotine coats the tube with a fine brown conductive layer. If the plastic cap isn't fitting snugly then replace it. Lastly, there could be a dry joint where the EHT wire connects to the metal clip that fits into the tube.
If the anode clip has got damp enough to rust, I would think the metal contact in the tube (that the clip makes contact with) might also be rusty.
Yes I did think that,it’s weird how this one went rusty,as it’s been in the house for about 10 years,and it appeared to be only the prongs as the metal further down that attached to the hv wire was fine