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Topics - Mark N

#1
The Newcomer's Forum / Orange Crush 12L (No Sound)
September 21, 2021, 11:21:22 PM
I have an Orange Crush 12L practice amp that suddenly stopped working around the same time my Danelectro Nifty Fifty (which I made another thread about) started malfunctioning. I get no sound through speaker or headphone jack.

This one has a 4558 as IC1 so I reused the trouble shooting from the Danelectro Amp (which uses an TL072, but I believe they have the same pin out) Using Enzo's helpful advice from the other thread I tested the DC Voltage on the pins and got

Pin 1: 0
Pin 4: -14
Pin 7: 13
Pin 8: 13

So I assume this IC has gone bad, correct? My understanding is that Pin 7 should read around zero. I tested the sound using an audio probe as well, I was able to trace sound from the input jack to a capacitor but then the signal goes to IC1. Testing the other leg of the capacitor I got no sound. I pulled the capacitor and was able to run a signal through it fine.

I plan on ordering another 4558 IC chip, but is there anything else I should be checking?
#2
Hi there!

I've had a late 90s Danelectro Nifty Fifty amp which worked for a couple of years and then after it sat for a while it developed an unusable distorted farty sound and a large amount of hiss.

It's got a volume and a gain knob. It sounds decent with the volume up and the gain on 1, but when you raise the gain then the problem begins. I can have the volume on 1 and the gain up midway and it becomes unusable.

It seems like it could be a grounding issue, but nothing looks out of place. The speaker vibrates with the noisy hiss/hum. First I pulled the Filter caps and tested them, then all the electrolytic caps, then the input jack, it also has 2 TL072 IC chips neither gets hot during use.

Anyone have any ideas? Or what I should check next?

***Also: The method I used to check the Electrolytic caps was (1) hooking them up to a multimeter setting it to resistance at 20v  and watching it go from 0 to infinity (actually with my multimeter it starts to rise and then at some point just goes blank) (2) Charging the cap with a battery and then watching it slowly drain using a multimeter (3) Popping it into my breadboard and passing a guitar signal through it to a working amp.

All of them passed #3. With method #2, some held a 9v charge (the filter caps) smaller caps held a smaller charge (which I assume is normal?) and method #1 Filter caps kept going high until the multimeter showed a blank screen. Some smaller caps felt like they blipped out after a small number (but since they did well with tests #1 & 3, I assumed it wasn't too much of a problem)
#3
Hey, there,

This is my first post. I recently picked up an old Sears Silvertone 1465 head as well as a Kay 765 for pretty cheap. They need some work. I've built pedals before, so I'm pretty sure it shouldn't be too hard. But I thought I ask here to see if anyone has worked on these before and had any tips or good resources to share. I have read up on draining the caps and other safety hazards. I doubt I'll be ever be working on it plugged in, but any safety tips would be appreciated.

Both are from the late 60's so information is a bit sparse. All I could find on the Kay is an old catalog. It seems like no one ever owned one. I did find the Silvertone Schematics online though. Anyways I was wondering...

1. How do I figure out the fuse type they need? (The Kay doesn't have it written. I know the Silvertone is a number 3) Also how do I know if the fuse is slow blow or instant?

2. How to I figure out the OHMS output for speakers? I have a multimeter, but I'm not sure what I should be checking.

3. Both have 2 pronged outlets that need to be replaced. I also have an old tube Harmony H-415 that needs a 3 prong plug as well. From my understanding, I drain the caps, then replace the plug with a 14AWG, replace the wires as they are and put the ground to the chassis(sanded down if there's paint) with a screw and a star washer so it will never come undone or loosen. Should I solder it as well or is that overkill? I figure it wouldn't hurt.

Any response/feedback/resources and or tips would be appreciated.