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Messages - Mark N

The Newcomer's Forum / Re: Orange Crush 12L (No Sound)
September 24, 2021, 10:49:11 PM
Thanks again, Enzo!

Flester, sorry to hear yours fell apart, but glad to see you reused what you could. This lil' amp does sound good. Once I get it fixed up I'm debating whether or not to keep it. I've got too many amps as is and I'd rather not have it keep breaking on me. It definitely is fun to play though.
The Newcomer's Forum / Re: Orange Crush 12L (No Sound)
September 23, 2021, 01:55:14 AM
Thanks for giving it a look, Willpirkle. Unfortunately, the 20L schematic is a whole different design. I did try to look for a schematic, but I don't believe anyone traced it. There aren't any diodes near the input. Audio signal goes through a capacitor, then resistor to ground before going into pin 5 of the IC chip. Pin 3 appears to just go to ground.

I didn't know over-voltage protection was a thing, but now I do. So that was helpful.
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?
Ha, That's what I was thinking. Thanks Enzo! You saved me some time poking around the components one by one.
Replacing IC1 did the trick. It's up and working and sounds good.

I did measurements and noticed pin 1 has a -1.9 reading. Anything to be concerned about?

On to my next amp to fix!
Assuming I did this correctly (Set the multimeter to DC Voltage, chose 20 as the value)

Pin 1: 0
Pin 4: -10
Pin 7: -9
Pin 8: 9

Pin 1: 0
Pin 4: -10
Pin 7: 0
Pin 8: 9

Phil: Thanks for the suggestion. I checked got 0 on both speaker connections.

Enzo: By what you said, IC 1, pin 7 is a problem area, correct?
Thanks for the reply Enzo and thanks for the interesting info about high voltage conditions. I didn't know about that at all.

I couldn't find a schematic online but IC1 and IC2 are TL072 op amps. There's 2 transistors as well and a five-leg TDA2030A power amp IC connected to a heat sink. I usually work on pedals so I don't come across stuff like this, please forgive/inform me if I'm not using the right term.

Also, I'm unsure of how to check for DC offset on any of IC output pins. I did a quick google and couldn't find anything. What's the best way to do this? A link to an article would be fine, I don't want to take up anyone's time. I greatly appreciate the help.
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)
I see. So I should be using a 3A then, correct?

Would it ever be necessary for me to switch the internal 5A?

If anyone needs an old Kay catalog. It's here:

From the description (on page 10). The Kay 765 head has 100 watts of output power and goes into two 12" speakers.

I have plugged the Kay into some speakers. I didn't get any guitar sounds but I did hear a faint hum sound. So that means the power transformers are good and there's a problem elsewhere.

JM Fahley: The thanks for your help. The Lamp Bulb Limiter seems like it will be useful. I have a question about the Silvertone Fuse type. The Schematic reads
"Fuse 3AG
5 Amp"

And the back of the head reads 3 AMP. I have always been using that suggestions on amps for fuses. What is the reason for the two numbers?
Also the Kay has 2 output (?) jacks on the back
Thanks for responses! I have not tried them yet because I wanted to know what speakers/Ohms and fuses to hook up before hand.

The Kay:
To start, I was told that they were not working. The guy I bought them from had said that the Kay did work but blew fuses. (I don't know what fuse he has in there and I want to make sure I have the right one before doing any work on it) I had plugged it in without speakers to test if the light came on. . It did. (If it didn't that would mean a problem with the power transformer (aka expensive problem), right? )

The Kay did have power, but also a fickle power chord that was cutting out. I also opened it up and poked around and found that a thick wire connected to the reverb had some tape on it. I undid the tape and found a wire insulated within another wire. The outside wire was not connected to anything. I assume it needs to be grounded. The other wire (which had been modified, probably fixed) goes to the TIP of the input jack for the reverb foot switch and is connected to one end of the reverb pot. The middle of the pot goes to the circuit board and the other end of the pot is the one not connected, (that I am assuming should be grounded) There is also no reverb tank so maybe someone gutted that and just left the wire.

I was told the caps on it were replaced. The looked new and had the price stickers still on them so I believe it to be true.

One reads " CE68
55V 3300uF
The other reads:
55V 3300uf
and I can't read the last line without pulling it out.

The Silvertone: I haven't plugged it in because it is missing the fuse as well as the fuse cap. Also when I opened it up I noticed it is missing a transistor on the 2nd channel. It also is missing the cardboard tube reverb tank that it is suppose to come with. I have a schematic that I found online of the 1465. I do not have it verified, I grabbed it off a message board while I was researching.

As for pictures all, I have is a crappy web cam camera which might not help at all. I'll see what I can do about borrowing a digital camera and snapping some pics of the guts. I understand that makes it a lot easier to see what I'm talking about. I really do appreciate any and all help/advice.

JM Fahley: How did you know the Speaker wattage for the Silvertone? And for the Kay is there anyway to test for the speaker ohms and wattage needed?

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.