G-7700 left channel crackle

Overundr1 said:
Basic soldering gear---
@30 watt iron
solder flux
0.32 lead solder
solder wick
rubbing alcohol
q-tips
good lighting

Get the board out where you can wriggle it around to access both the back and front sides.
The two caps in question are non polar, the originals should have markings (bp) on their sides and can be replaced without concern as to which lead goes where.
The vd1212 diode will look like a small silver/red ball on thin leads ASK here before replacement for details (one step at a time).
Finally the transistors have to go in only one way (out of six combinations) again ASK before starting please.
Should be a cool project for you and younger edition and an easy way to get started in your own maintenance skills.
Pictures as you go along are a bonus :)
-Lee
Click to expand...

I have a 25 watt iron and some ""44" rosin core (whatever that is) solder material. Can anyone tell me if that is good enough?
 
I looked into the "44" solder it seems to be OK to use so I went ahead and replaced C07 & C08 with the new 50v 10uf caps.

Now on to D01 to replace VD1212 with the 1N4148. How do I know which direction to insert it?
 
Vintagear said:
I looked into the "44" solder it seems to be OK to use so I went ahead and replaced C07 & C08 with the new 50v 10uf caps.

Now on to D01 to replace VD1212 with the 1N4148. How do I know which direction to insert it?
Click to expand...

The PCB is marked with the orientation of the diodes (triangle pointing to a narrow rectangle). The rectangle corresponds with the end of the 1N4148 that has the black band on it.

ca1010vd1212.jpg
 
Great, thanks!! I'm on it.

Can you tell me what the next step is based on the other parts I ordered?
 
Actually I'm confused, should the black band on the new diode be on the same side as the black half of the old diode? Because it looks like the arrow is pointing to the red side of the old diode.
 
Black band on 4148 to pointy end of triangle symbol.

Before continuing please post the position and number on the transistor for the following locations on the board to be sure we are both on the same page---

example

TR01 1845

tr01---
tr02---
tr03---
tr04---
tr05---
tr06---
tr07---
tr08---


Do not remove any transistors yet, we still need a discussion on lead orientation and I want to verify there are no errors in the schematic I am using before we dive in.

-Lee

Pics would be a help too
 
Oh no... I think I killed my receiver. I take full responsibility for my bone-headed move.

My son put the caps in with no problem, then we soldered the diodes in series (like Pete's pic) but I screwed up and had him put the diode with the black end on the same side that the black end was on the existing diode (opposite the arrow point). Like a couple of knuckle-heads, we thought everything looked good (solder-wise) and I pressed the power button. It came out of protect, I pressed the tone defeat/on switch and "poof" I saw the magic smoke. It looked like the fizzle/smoke came from the center of the amp. I don't see any parts or areas that look burned or damaged.

Is my unit toast, or is there hope.
 
Pull the tone board back out and post up a picture. No such thing as toast and btw we all have been there done that.
-Lee
 
Here are some pictures of the Tone Board (F-2855) Power Amp Board (F-2980) and Power Supply Circuit Board (F-3060). The only part that looks a little weird is in on F-2980 next to a large resistor (R-617 next to it looks a little charred (could be old stuff or dried Deoxit?)


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These pis were taken right before the mishap. Now you can see why I want to save my G.

Plus it's been with me since it was brand new. How could I give up on it now?
 

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Nothing jumps out from the pictures. I suggest measuring the resistors on the tone board. Also might be a great time to build yoirself a dim bulb tester to prevent further mishaps.
 
I think I'm out of my league. I don't have the equipment or the knowledge to measure the resistors. Can you walk me through it? If not, can someone recommend a reputable tech in the NYC tri-state area? Or a reputable AK'er I can send it to if it comes to that?
 
Answered your PM.

In any event, if the diode was D01 and D02 on the tone board (F-2855), then the damage depends on if you had the diodes properly in series (cathodes facing the same way) or if you botched it (cathodes facing towards each other). Rather than try to sort out exactly what happened, as long as the +/-33V supplies were not damaged, then we're probably talking about TR03, 04, 05, and 06 needing replacement, and maybe a few resistors. There's a possibility that a enough of a DC thump was sent to the power amp to cause a problem, but powering up with a DBT will save this unit from any further damage to the amp.
 
Thanks for the PM reply. I reached out to him and am awaiting a response. The cathodes were facing the same direction, but I think my mistake was putting the black side of the (in series) diode away from the point of the triangle. I saw the black side of the existing diode in that direction and made the incorrect assumption. I had only changed the 2 caps and the 1 diode (D01). I think the sizzle and magic smoke came from the amp board area but am not sure. Would that be bad news if it came from the amp board?
 
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