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Problem with fan on Ilford Multigrade 500H enlarger head

Photopathe

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Hi! This worrying thing started to happen with the fan on my Ilford Multigrade 500H enlarger head. First the safelights started not to turn off when printing. Now the fan will not turn on when printing. The fan will still turn on when initially turning on the power on the enlarger. In both cases the problem was intermittent at the beginning but is now constant. I need to mention the controller I use is not the original but the RH Designs. I bought the controller new about 2 years ago.
Is the problem likely to come from the controller or from the head itself?
What can I do about it?
Thanks in advance for any input!
 
My assumption is the fan is controlled by the power supply, but it could also be the controller. I'm 99% sure it's not in the head since I've taken one of those apart in the past and don't recall seeing any timing circuit. Plus you're having safelight issues, which are not related the head. RH Designs should be able to confirm whether the controller has any role in activating the fan or safelights. You can surmise the fan itself still works since it turns on when the system is turned on, so I would focus on the issue being in the power supply or the controller. If you have the original controller you could test with that. Figuring out which of those components is failing would be my fist step.
 

Thanks for your reply! I also wrote to RH Designs last Sunday. I am still waiting for a reply. I wrote again today. Will update this post once I have something new.
 
There is a Rifa capacitor / cap in the head that is prone to failure, I think it is used for noise suppression in line with the fan. This may be on the way out and causing your problems perhaps.
 
The power for the fan and controlling the safelights comes from the PSU.

If you have the RH controller connected to the Ilford PSU and the PSU connected to the fan/lamps/safelights, then i'd suspect the PSU.

In the Multigrade 500H system the PSU is more than just a transformer and the control electronics could be showing their age now.

Mike
 

What would be the best solution in this case? Buying another old one used doesn't sound like a very promising solution...
Still no reply from RHDesigns. Maybe they are on vacation. I don't suppose opening the PSU to see if it needs some dust removing could be of any help?
I find it somewhat comforting to think that the "new" RH Designs controller is not the faulty component.
 
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Unless you are very competent with fault-finding electronics and have the service manual, then the only option would be to swap out the PSU.....assuming you can get hold of one.

Inside the PSU, there are a couple of 20mm glass fuses if i remember correctly, so they might be an obvious check.

Mike
 
Strange things happening. During the last two printing sessions everything works as it should again. Not complaining about it of course but I assume the problem is bound to come back sooner than later. I opened the PSU to check for dust as someone pointed out there could be an accumulation of dust over the years that could interfere with proper operation. To my surprise there was not much. It was quite clean. I still have no reply from RH Designs. Disappointing after sale service to say the least. I just sent a message to Second-hand darkroom supplies in UK as I remember they used to answer queries quite quickly and they do sell and give support for RH Design devices. At least I asked if they could confirm if either the original PSU or the Analyser control the safelights and the fans.
 
Firestarter said:
There is a Rifa capacitor / cap in the head that is prone to failure, I think it is used for noise suppression in line with the fan. This may be on the way out and causing your problems perhaps.
Click to expand...

I hate to jump on an old thread, but this one seems like the most promising lead for something I'm currently trying to figure out.

I've been playing around with an Ilford 500H head, and that Rifa capacitor just exploded on me.
I'd like to replace it, but I'm not sure exactly what its specifications are. (The service manual PDF doesn't really give a detailed bill-of-materials.)

Do you have any idea?

From the fragments I've collected so far, I think its 0.25uF, and obviously an X-rated capacitor. But beyond that, I have no idea. Its likely that any X capacitor in the ballpark that's rated for the right line voltage should be fine, but I'd still like to know what is supposed to be there.
 
Okay, I know I'm replying to myself here, but I've spent more time looking at the fragments and searching the various numbers I can read.

Its a RIFA PMR-2026 0.25uF capacitor, which is rated for 250VAC. Only unknown is the ESR (series resistance; it comes in a range of variants), but from what little I can read I think its either 100 ohms or 150 ohms. (Modern X capacitors seem to have an ESR closer to 0.1 ohms.)

In any case, I think I'm just going to replace it with a modern 0.22uF X-rated capacitor. May not be an exact match, but its just a line filter cap for the fan, so it should be fine.


mpirie said:
Do you have a photo of the location of the capacitor you can post?

Mike
Click to expand...
Its in the fan tray at the top of the enlarger head assembly:

I apologize for how disgusting this area looks in the picture. My head is nothing but a pile of dust and rust, but I got it more for tinkering than actual use. I'm obviously going to do a little cleanup before fixing it.
 
I think you're on the right track.....it just looks like a filter across the motor.

It's possible Ilford just used whatever caps were available at the time during the build.

Mike
 
I will have to check for you. I made a note somewhere. It is a capacitor and a resistor encased in a resin. If your one blew I guess you got a whiff of the disgusting odour they put out
 
Firestarter said:
I will have to check for you. I made a note somewhere. It is a capacitor and a resistor encased in a resin. If your one blew I guess you got a whiff of the disgusting odour they put out
Click to expand...

The odor mine made honestly just smelled like campfire smoke.
Anyways, the fragments I collected afterwards looked like just the Rifa capacitor noted above. If there was a resistor in there, I didn't see it.

AFAIK, the main reason to even have a resistor across the leads would be to discharge that capacitor more quickly after unplugging the head, and probably not a big deal to not have in that part of the assembly.

In any case, I replaced it with a modern 0.22uF X capacitor and put the assembly back together. (after blowing out and vacuuming up a lot of the gunk in there)
 

Great, hope it works out ok for you. Just for information anyway what came out of mine was a 0.25 uF 630 V cap and a 47 ohm 1/2 watt resistor.... at least that's what I worked it out to be from the colour bands..
 
Firestarter explaining a blown-up capacitor causing disgusting campfire smoke odor..... makes perfect sense!
 
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