Print

[K8AC]

I have a dial bulb out in my Alpha 89 and I understand that at some point in production the bulb voltage changed from 12V to 28V.  Anyone know when that occurred serial number wise?  My serial is 94140122. 


73, K8AC

[W5RG]

I'm not sure when it was but I ordered a few for mine from Mouser and they work fine..I pulled the manual up on line and got the part number..not hard to change out just pull the front panel off..I need a new inside fan for mine soon..Bob

[K8AC]

Well, it turns out that mine are the 28V bulbs.  Was able to tell by the fact that the zener diode that regulated the voltage down to 12 was not present on my board - outline was there, but no diode.  Instead of ordering the bulbs, I put a couple of frosted bright white LEDs in place of the bulbs with a 5.6K resistor in series.  About the same brightness level as the bulbs, but won't have to worry about replacing one again.  My manual shows two part numbers for the bulbs - probably one for 12V and one for 28V. 

Not sure how difficult it is to replace the blower in your amp.  I replaced one in my Alpha 86 years ago - probably about the same chassis layout.  I recall that was not fun. 

73, K8AC

[AE0Q]

I have a dial bulb out in my Alpha 89 and I understand that at some point in production the bulb voltage changed from 12V to 28V.  Anyone know when that occurred serial number wise?  My serial is 94140122. 
73, K8AC

Alpha 89 Dial Lamps:

There is no record from ETO of when the Control Board was changed to use 12v lamps.
Unplug the 89 from AC and remove the cover. Shine a flashlight down into the slot on the right side of the front sub-chassis and look at the Control Board.
If the two parts circled in the photo are missing, then it has been modified to use 14v CM73 lamps.
If the diode and resistor are still on the board it will use 28v CM85 lamps .
The lamps fail either from shock or vibration (moving the amp) or from lots of turn-on cycles, like any incandescent lamp.
The knobs and front panel have to be removed to replace the lamps behind the dial plates.

Glenn AE0Q
Alpha RF Systems

https://drive.google.com/open?id=16R-vVe2nhDAKZcR6MVjUGvbjs1Vau3UE

[W5RG]

Thanks Glenn..That is good information..mine were the 14 volt type and they were not had to replace..The 89 is sure a good amp..really happy with this one and very quiet blower..Not looking forward to replacing it..looks like I would have to pull the back panel..You did the right thing replacing with LED's..73s Bob