President hr2510 display shows 8

[komppa]

Hi!

I've tried to fix my old President hr-2510. Radio has been in the garage for a long time (25-30 years) and now I powered it on and display was full of number 8 (with background light). Still I can hear stations.

Here is couple of things what I have already checked (I don't know anything, google told me everything)

• I measured voltage regulators from CPU board: IC311 gave 5 V and IC312 gave 8 V. I googled it and if I understad right -> regulators are ok. Power supply gives 13.6 V.
• I checked all soldering points. They look quite nice.
• I think capasitors haven't "exploded"
• I make sure that J304 (9-pin) goes to the display
• I've googled but I don't know what is the problem¨

It might be possible that radio has modified (Frequency Conversion, Power mod?)
I'm not sure because radio is used.

This has helped me a lot
Rogerbird's Radio Modification Information
http://rogerbird.tripod.com/


Few images from CPU board

IMAGE 1
http://aijaa.com/In129w
IMAGE 2
http://aijaa.com/KM56W7
IMAGE 3
http://aijaa.com/2NOsk0


And if someone has a tip how to rip off switches to get plastic front cover off would be awesome. There is no more screws.

Thank you!

 

[Robb]

If that radio worked 25-30 years ago the last time you used it; then I would immediately suspect that a few electrolytic caps on the board are failing and some have failed outright already. Sounds to me that a cap on the display board may be shorted - first blush.

I've restored many radio that were that old, and even slightly newer, by replacing all of the electrolytic caps. I found that after testing all of the old caps that they were either in a state of failure or very near to that mark. Some of the larger caps were still OK; but the mid sized/small caps were weak or outright bad.

Even if the caps themselves are not the failure, it may still need to be done purely because of their age and lack of quality.

You can buy cap kits online from Ebay, or send the radio to a shop and have them go thru it for you.

 

[komppa]

Thanks for replying!
In fact, 25-30 years ago there was something wrong with the transmission (2 voltage regulators on main board?) And screen was already broken.
But still it could be possible that capasitros are broken.

73
komppa

 

[Radio Tech]

I pay close attention to those caps on the cpu board. They leak after all this time and start to eat the circuit traces away. Also old glue on the cpu board becomes conductive over the years.

 

[AudioShockwav]

X2 what radio tech has posted. Use the Forum search feature, you will find many threads about this now common fault.
Old caps and old glue often are the problem.

73
Jeff

 

[komppa]

Thank you for helping!
Firstly I am going to replace all capacitors on cpu board. If glue has became conductive what would be best way to clean it off?

 

[Radio Tech]

That glue can be very hard like epoxy. A good heat gun will aid in making it pliable. Then use something to pick it off. Dental pic ect. Be careful not to over heat the board and cause components to fall off. Use 99% IPA to clean the board when done. Inspect the traces around the nodes where the caps where.

And also use caution removing components. Being 30 years old it will not take much to lift traces and pull vias out.
Good luck on your project.

 

[komppa]

This picture is from my hr2510 cpu board
http://aijaa.com/In129w
There isn't any glue so glue as a conductive material cannot be a problem.
Still I`m gonna clean board with alcohol.

On the display board there is 3 capacitors should I replace them?

Best regards
Komppa

 

[Radio Tech]

This picture is from my hr2510 cpu board
http://aijaa.com/In129w
There isn't any glue so glue as a conductive material cannot be a problem.
Still I`m gonna clean board with alcohol.

On the display board there is 3 capacitors should I replace them?

Best regards
Komppa

That is good there is no glue.
All capacitors should be replaced. No question about that. Should be 16 on the cpu board alone.

 

[komppa]

That is good there is no glue.
All capacitors should be replaced. No question about that. Should be 16 on the cpu board alone.

Ok, I will write project updates how its going.

73
Komppa