New Member SCR8 issues.

[Lino]

Hello All,

new member here from Toronto, Canada. I've been reading through a lot of your posts and am both inspired and impressed. A great resource for a newbie like me.

Thank you all!

Going to jump right in and ask for help/guidance or any insights any of you can offer.

I have an SCR8 currenty in pieces on my table. I've replaced the belts, installed a new idler, fixed the pesky broken transport bit of plastic that notoriously breaks and now am dealing with a power issue. I'm afraid I've exhausted my limited knowledge and am reaching out.

Issue: I blew something in messing around and as a result am getting low voltage at my cassette motor. 2.5V to be exact. I can get the motor to spin and transport to engage by attaching leads from a 9V battery.

Transformer output is 14.5-15V I believe. Verified with a meter.
Radio working and getting hum and statice from Tape and Aux when selected.

Whatever I blew up has also effected some of the lighting. The Battery/Tuning/Record LEDS and the FM stereo indicator.

I have just enough knowledge to do more damage so I'm pausing and looking for help.

Any thoughts? I'm sure I've only scratched the surface in diagnosing this issue so fire away. Happy to learn from you all.

Some pics of it's current state attached.

 

[Tinman]

It could be the power button/switch.
You could try verifying voltage there.
I've had to desolder, remove and physically clean the contacts on the inside on a few of them because Deoxit wouldn't do it.
Also, the Marcan and lesser named capacitors (even the Panasonics) can be a problem on these.
I've owned seven of these and a GE 5259 over the years and recapped most of them.
I just bought another SCR-8 and plan on recapping it this winter.

 

[Lino]

Hey Tinman,

thanks for the info. Is there a way to diagnose the power switch without pulling it out? Would a problematic switch still allow power to get to the rest of the box? Or is it potentially just not providing enough voltage? I'm pretty new to this and am practicing desoldering on a scrap board at the moment. Once I'm comfortable I'll likely change some of the caps. I'm weary to try it on this just yet.

 

[Tinman]

On a second reading, you wrote that you think you blew something.
Check the resistors R164 (4.7 ohm) and I believe it's R204 (2.2 ohm).
They should be fusible resistors (usually gray in color).
One might have blown.
You might have to lift one of the legs to test.

 

[Lino]

Great, will do. I pulled the cap off the power supply today and it tests bad. I think. Was getting variable reading and nothing greater then 700 microfarads. Supposed to be 2200. I’ll start there. Have new ones coming tomorrow. And I’ll check the two you’ve suggested tomorrow. I may just go ahead and replace a bunch as I get more comfortable with the process. Thanks Tinman. Appreciate the help.

 

[Superduper]

You possibly blew or damaged one or more regulators while working on it live. Capacitors could fail but they generally fail over time, not acutely unless subjected to overvoltage or reverse polarity. Low capacitance wouldn't generally present in the power supply circuit as low voltage, rather will have poor regulation and additional ripple. For the motor drive, try changing Q204 and D208 (10.2V) zener. For the led drive circuits, they are regulated by Q104 and D108 (9V zener).

 

[Lino]

Ok, thanks. I’ll check those out too. Quite the learning curve this hobby. Also is it common for there to be this much adhesive on the boards? See attached files. Seems excessive.