HH HA100S, 1970s 5ch stage amp

[N Cook]

Asked to rennovate the controls and replace the blown front panel bulb.
Open up and amazed to see the illumination is by phosphorescent panel
powered directly
off the 240V mains. I would like to strip out and replace with a string of
low V filament green lamps,
but the owner wishes retained. Gives a distinctive magic-eye/ CRT
phosphorescent glow behind
each of the controls through the perspex front cover. "blown" bulb due to
flexing of the conductor strip so
too far from the phosphor material to activate in that area, probably due to
a knock on the front perspex.

Anyone familiar and care to comment about the
safety aspects especially if powered from neutral / live swapped mains
supply etc

electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse

 

[Graham]

Asked to rennovate the controls and replace the blown front panel bulb.
Open up and amazed to see the illumination is by phosphorescent panel
powered directly
off the 240V mains. I would like to strip out and replace with a string of
low V filament green lamps,
but the owner wishes retained. Gives a distinctive magic-eye/ CRT
phosphorescent glow behind
each of the controls through the perspex front cover. "blown" bulb due to
flexing of the conductor strip so
too far from the phosphor material to activate in that area, probably due to
a knock on the front perspex.

Anyone familiar and care to comment about the
safety aspects especially if powered from neutral / live swapped mains
supply etc

Reminds me of those phosphorescent square panels that were mounted behind a
light switch so you could locate it in the dark and operated on the mains
voltage across the open switch.


--
Graham.



%Profound_observation%

 

[NSM]

| Asked to rennovate the controls and replace the blown front panel bulb.
| Open up and amazed to see the illumination is by phosphorescent panel
| powered directly
| off the 240V mains. I would like to strip out and replace with a string of
| low V filament green lamps,
| but the owner wishes retained. Gives a distinctive magic-eye/ CRT
| phosphorescent glow behind
| each of the controls through the perspex front cover. "blown" bulb due to
| flexing of the conductor strip so
| too far from the phosphor material to activate in that area, probably due
to
| a knock on the front perspex.
|
| Anyone familiar and care to comment about the
| safety aspects especially if powered from neutral / live swapped mains
| supply etc

Sounds cool. It wouldn't bother me. Since there's no ground (earth)
involved, swapping the line leads will have no effect, which may not be true
for the rest of the system. If it isn't broken, don't 'fix' it.

N

 

[N Cook]

| Asked to rennovate the controls and replace the blown front panel bulb.
| Open up and amazed to see the illumination is by phosphorescent panel
| powered directly
| off the 240V mains. I would like to strip out and replace with a string of
| low V filament green lamps,
| but the owner wishes retained. Gives a distinctive magic-eye/ CRT
| phosphorescent glow behind
| each of the controls through the perspex front cover. "blown" bulb due to
| flexing of the conductor strip so
| too far from the phosphor material to activate in that area, probably due
to
| a knock on the front perspex.
|
| Anyone familiar and care to comment about the
| safety aspects especially if powered from neutral / live swapped mains
| supply etc

Sounds cool. It wouldn't bother me. Since there's no ground (earth)
involved, swapping the line leads will have no effect, which may not be true
for the rest of the system. If it isn't broken, don't 'fix' it.

N

The phosphorescent material is coated on a 2 inch by 24 inch metal sheet
which is connected toi neutral. Surrounding the edge of this isolating it
from the chassis is thin plastic which I would not like to rely on if
swapped to live side.
Was thinking , anyone know what would happen if you connected a 240V / 12 V
transformer back-to-back to 12V/240V transformer to give an isolated 240V
supply?

 

[Asimov]

"N Cook" bravely wrote to "All" (02 Dec 04 07:38:41)
--- on the heady topic of "Re: HH HA100S, 1970s 5ch stage amp"

NC> From: "N Cook" <[email protected]>
NC> Was thinking , anyone know what would happen if you connected a 240V /
NC> 12 V transformer back-to-back to 12V/240V transformer to give an
NC> isolated 240V supply?

Some loss depending on the core size. You likely won't get exactly
240V out under load and the 12 volt lines, if long, will have to be
thick to minimize IR losses. In a pinch it's okay for line isolation.

A*s*i*m*o*v

.... Power is obtained by current meeting resistance

 

[NSM]

| The phosphorescent material is coated on a 2 inch by 24 inch metal sheet
| which is connected toi neutral. Surrounding the edge of this isolating it
| from the chassis is thin plastic which I would not like to rely on if
| swapped to live side.
| Was thinking , anyone know what would happen if you connected a 240V / 12
V
| transformer back-to-back to 12V/240V transformer to give an isolated 240V
| supply?

If the device has a double pole switch which controls the panel, no problem.
If not, and the panel is fed via a resistor, split the resistor into two
parts and put one in each lead.

N

 

[VMI]

Hi,
FWIW, a link to spares and schematics for HH amps:
http://www.majelectronic.co.uk/index.htm
Cheers,
Marco

 

[N Cook]

Hi,
FWIW, a link to spares and schematics for HH amps:
http://www.majelectronic.co.uk/index.htm
Cheers,
Marco

I posted to r.a.r+p and suggestion this material is zinc sulphide.
Also suggestion about using computer gizmo electroluminscent panel and
it looks as though the rope/string version can be formed into tight loops
around the pot shafts which would probably work well enough.
Perhaps blue rather than green but easier than 17 bulbs and give
better even illumination around each knob 'skirt'.
Could even be sound activated for more 'go faster' perzam.

electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse