Ah ha! You have a service manual. Now I understand.

Dick

On Fri, 18 Mar 2005 17:36:28 -0600, Robert Kubichek
wrote:

In the sevice manual, the junction of R77-R78-Q12 is 11.5v and this goes
out to the lamps.

Bob N9LVU

Dick wrote:
I sure don't see that Bob. The lamps are driven off the collector of
Q12. This voltage varies in accordance with the light received by R3.
I don't see any reference to voltages at all anywhere in that
circuit..

Dick

On Fri, 18 Mar 2005 15:53:06 -0600, Robert Kubichek
wrote:


If you look at the schematic, you will see that there is 11.5v supplied
to the lamps for the display, ANY grain of wheat lamp rated for 12-15v
will work. Radio shack does sell them, most older Icoms IC229H ect use them.

Bob N9LVU

Dick wrote:

My problem is I had to disassemble the radio so far to get to the back
of the lamps, I can't run it to check the voltage. The lamps are
driven by an automatic dimmer circuit, so can't just trace the source.
Would like to see a data sheet on the lamps, but doesn't seem to be
available. I saw one reference to Intersil as the manufacturer, but
it's not listed on their website.

Dick

On Fri, 18 Mar 2005 13:59:07 -0600, Robert Kubichek
wrote:



Try Radio Shack, as they had some grain of wheat bulbs at various voltages.

Bob N9LVU

Dick wrote:


My Icom IC-28H has gone dark. Looks like both lamps are gone. The
schematic lists these lamps as HRS-7219A-G40. I found a couple of
places that had minimum orders of $100 and $300 respectively. That's
out. I read a message on eham.net where a ham had replaced these
lamps with amber LED's and appropriate resistors. Anyone done this?
Other options?

Dick - W6CCD