dash pad lighting control location

[flysamo]

hear a loud pop when using dash pad lighting was turned full up, there appears to be two parts of the control ckt for a early Ovation, the reostat on right side of panel and the transistor control unit to provide adjustable power to the pad lights and instrument panel lights. can some body provide location of transistor control unit for lighting. 

[PT20J]

9 hours ago, flysamo said:

hear a loud pop when using dash pad lighting was turned full up, there appears to be two parts of the control ckt for a early Ovation, the reostat on right side of panel and the transistor control unit to provide adjustable power to the pad lights and instrument panel lights. can some body provide location of transistor control unit for lighting. 

On my 94 J it’s in the tail by the battery. 

[Yetti]

In the F it is screwed to the top of the nose wheel well.

[flysamo]

thanks for the information, this is the 4th time we have had the unit( a 1960 design) go bad over the years, transistor cant handle the load, over heats nice to have lights when doing night flying. a top notch avionics shop recommend a faa approved unit, Seaton Engineering Mini dim units, for panel lighting, resettable and can handle all types of lighting from led to old fashion light bulbs. time to update to a newer design.

Edited December 17, 2020 by flysamo

[PT20J]

The fact that you’ve had so many failures coupled with the loud “pop” sounds like you might have a short somewhere. The bulbs don’t draw a lot of current and transistors don’t make a sound when they blow.

If you do replace the dimmer, I’d get a pulse width modulated one that will dim LED lights as well as incandescents.

Skip

[flysamo]

does any body have a schematic or the best place to obtain schematic wiring, that shows wire to transistor power regulator wiring in rear avionics compartment, 3 wires tie into the regulator  for panel pad lighting on early ovation

[flysamo]

8 minutes ago, flysamo said:

does any body have a schematic or the best place to obtain schematic wiring, that shows wire to transistor power regulator wiring in rear avionics compartment, 3 wires tie into the regulator  for panel pad lighting on early ovation

agree pulse width is the way to go, sixty's teck has been surpassed by todays technology

[N201MKTurbo]

On 12/17/2020 at 8:18 AM, PT20J said:

transistors don’t make a sound when they blow.

When i was a kid I worked for car stereo amplifier company (Orion Industries). I designed the power supply for a 2KW amplifier. There were quite a few times while debugging that all 27 MOSFETs went off at once. I can assure you that some transistors do make noise when they blow.

[carusoam]

We have an email for techsupport@mooney.com (or something like that)...

That may be an avenue to receive said document (?)

Best regards,

-a-

[jcovington]

On 12/18/2020 at 8:35 AM, flysamo said:

does any body have a schematic or the best place to obtain schematic wiring, that shows wire to transistor power regulator wiring in rear avionics compartment, 3 wires tie into the regulator  for panel pad lighting on early ovation

See if the attached drawing is what you are looking for. It is from the information that I have for my 1996 M20J. I suspect it is similar to yours as the later J share a lot in common with the long body planes.

The first page of the drawing is where I have extracted just the wiring for the lights from the aircraft schematic so it is easier to follow. The second page is the internal wiring for the control box in the avionics bay that I did when mine failed the first time. The part that fails is the LM338 voltage regulator (power transistor). The LM338 as well as the diodes are readily available.

If you decide to repair your box the only really tricky part is the transistor output is the case. The control box has plastic spacers and insulators to keep the transistor case from contacting the control box case to avoid shorts to ground. The transistors have to be unsoldered from the board to remove the board to gain access to the nuts, spacers and bolts that hold them on. Reassembly is fairly easy after the transistors are remounted.

The box in my airplane has failed twice. The first time was a buzzing that got worse over time until I replaced the transistors. The second time the panel lights just quit working.

Jim

Panel Light Connections.pdf