Today I received two cards that came from some sort of scrap lot and both are missing components that I have a hard time identifying.
GUS MAX:
Capacitor C19 had a leg ripped off. What I can still read is: K5R 562J. What are the specs of this capacitor? I couldn't find a way to decipher it...
Roland SCB-7:
FL3 and FL4, see photos below. These are probably filters on the +12V and audio output lines. The other filters that are still OK are labelled F103.
After some extensive googling I found this part by TDK that comes in a smaller package, but seems to be somehow similar: https://product.tdk.com/info/en/documents/cat … r_ach32c_en.pdf
But I am not sure whether it really is a suitable replacement part (besides being EOL by now).
You can just short the outer pins of the filters on SCB7 to make it work again and maybe eventually you can find suitable replacement parts to restore visual condition.
If the capacitor footprint on GUS is one of those small orange ones it'll be a 0.1µF radial ceramic capacitor. It is quite unlikely the capacitor plays a critical role as most are simply power supply bypass ones and lack of one or two won't make a difference in operation. I was unable to see on photos where the C19 is though...
You can just short the outer pins of the filters on SCB7 to make it work again and maybe eventually you can find suitable replacement parts to restore visual condition.
Good to know. I was thinking about a temporary fix like that too, but wasn't sure whether I'd fry something if I just bridge these pins.
If the capacitor footprint on GUS is one of those small orange ones it'll be a 0.1µF radial ceramic capacitor. It is quite unlikely the capacitor plays a critical role as most are simply power supply bypass ones and lack of one or two won't make a difference in operation. I was unable to see on photos where the C19 is though...
Yeah, one of the small orange, radial ceramic ones. I attached some photos. Maybe I'll just put the card in and see whether it operates normally or behaves funky...
TDK's ACF451832-103-TD01 is a suitable filter replacement for those missing on the SCB-7.
I performed a similar repair on an SCB-55 several years ago:
Fantastic, thank you! I think I came across this part during my research but for some reason scrolled over it... Now I'll just have to find a supplier that will sell in household, not industrial-sized batches, and that won't charge me an arm and a leg for shipping. Duh...
EDIT:
Here's a datasheet that could match the capacitor: https://www.datasheetarchive.com/pdf/download … 520K5R%2520104K K5R on the ceramic capacitor seems to decode to: K - Capacity Tolerance +/- 10% 5 - Rated Voltage 5-50V R - Dielectric X7R (Stable)
562 would then, according to the datasheet, be 5600pF = 0.0056µF = 5.6nF
But I might be wrong...
Last edited by gex85 on 2020-09-10, 17:53. Edited 1 time in total.
The C19 is a bit different, it is a filter cap on a signal line. Luckily the one right above it is the right kind. I expect it to be 1000pF range rather than 0.1µF. Try to see the markings of the neighbor.
The C19 is a bit different, it is a filter cap on a signal line. Luckily the one right above it is the right kind. I expect it to be 1000pF range rather than 0.1µF. Try to see the markings of the neighbor.
Okay, that would be roughly in the range of the values I found in the datasheet (see my EDIT on the bottom of the above post). That would make it a 5600pF one.
Okay, cool, I have just ordered the filters and the cap + some other components I needed for other cards. Still, shipping is more expensive than the components themselves, but that's life.
Thank you very much for your support. I will report back when I have repaired the cards.
That is two inductors with cap in middle. Can be made same way using individual components and little wire to connect them together, Between two inductors in series, with capacitor in middle and capacitor is grounded. Basically power filters.
Okay, that would probably look a little "ghetto" but since I have found suitable replacement parts there's currently no need for such a hack. However, someone might find this hint useful in the future!
Today I tried the Ultrasound and it works as expected (though I am not familiar with the GUS at all so I wasn't exactly sure what to expect...). But it does output sound on both channels and doesn't sound distorted or garbled or noisy. So that's a huge win!
On the Roland SCB-7 I have bridged the missing filters but didn't have the time to test it yet...
The capacitor on the GUS MAX has been replaced as well. I was a bit in a hurry so I just soldered it in on the back of the PCB, should have paid more attention...
