I bought this unit for parts and was able to traced out an issue with a voltage regulator that got it playing music again. However, the screen is very faded. I did the simple item of checking the solder connections for the display. But I think it is backlit by a bulb and that bulb has gone bad. Below are some photos.
You can see the bulb I am referring to in the second image. I am not sure how to deal with that. It looks like it is self contained and I don't want to destroy the display trying to get better lighting, but I would like to fix it if its possible. The other though I had was to jerry-rig an led next to it to pass light in, though that seems like a bastardization in this unit.
Anyways, I've attached a service manual for the unit if anyone has any thought of repairs or things to check.
Best regards!
You can see the bulb I am referring to in the second image. I am not sure how to deal with that. It looks like it is self contained and I don't want to destroy the display trying to get better lighting, but I would like to fix it if its possible. The other though I had was to jerry-rig an led next to it to pass light in, though that seems like a bastardization in this unit.
Anyways, I've attached a service manual for the unit if anyone has any thought of repairs or things to check.
Best regards!
Relying on my own experience, VFDs are not repairable when faded like this. Only way is to replace it with a fresh one, I suppose McIntosh will supply it.
VFD's often suffer with power supply issues due to the way the negative rail and 'floating' filament supplies are derived. Typically the cause is failure (deterioration) of the electrolytic caps in that area of the supply. That would be the first thing to check before condemning the display itself.
Also if the display has sat unused for years the segments may appear dull but can increase in brightness with use. There is often a 'test' pin on the display driver chip to enable all segments as a test.
Also if the display has sat unused for years the segments may appear dull but can increase in brightness with use. There is often a 'test' pin on the display driver chip to enable all segments as a test.
Thanks for all the good information. I have reached out to McIntosh to see if the part is available. I also let the unit sit on for a few hours, but I didn't see improvement. Not sure if that process is hours or days. I still need to look for the test pin and there is one cap in the area I will test and get ordered.
I did find this when I was enlightened it wasn't a LCD. https://www.hpmuseum.org/forum/thread-17062.html.
Is this a process anyone has experience or thoughts on?
I did find this when I was enlightened it wasn't a LCD. https://www.hpmuseum.org/forum/thread-17062.html.
Is this a process anyone has experience or thoughts on?
You normally see them brighten after a few hours if it is going to make a difference.
There are always hacks and tricks to try. You can over run the filaments to try and burn off any coating and improve emission and you can also increase the voltage to the display to try and inprove emission from the surface of the segments.
This is from a Sony but is typical and all VFD's use a similar arrangement although this one also has a transistor regulator. The electrolytic caps are common failures, the filament supply (top left) is floated to the negative rail via a Zener and the Zener voltage can be tweaked to give a higher differential between filament and negative rail. Nothing else ever seems to fail, its always caps.
