My First Phase Linear Restore- New Guy to the Forum

[jbeckva]

Solder in some sockets, takes the stress off the traces too. Get the good machined sockets...a cheap socket will be a frustration.

Are these IC's for the 2000 the ones that need the browndog adapters?

 

[mjstriker]

Are these IC's for the 2000 the ones that need the browndog adapters?

Yup so I should be able desolder the smaller op amps off the adapter and replace with the new ones without removing adapter. At least that's the plan in theory

 

[laatsch55]

You gonna desolder those surface mount miniatures and resolder ?? Lord....

 

[mjstriker]

You gonna desolder those surface mount miniatures and resolder ?? Lord....

I figured it is worth a go. I have a fine tip and a little experience soldering integrated ram chips to motherboards so I figured what the heck

 

[jbeckva]

I figured it is worth a go. I have a fine tip and a little experience soldering integrated ram chips to motherboards so I figured what the heck

Ram chips.. yeah ya can do it. Got a scope or mag glass/light?

 

[mjstriker]

Ya I have a magnifying glass. Before getting into amps and stereo I used to modify/repair gaming consoles as a side job. One of the big upgrades was adding more ram but it was all integrated. I would end up taking the chips off old garbage units and soldering them into new ones. Those were like 30 pins each. Pain in the butt

 

[mjstriker]

Worked on the 2000 a little bit today.Added the Zeners to rectifier diodes and it brought down the voltage quite nicely to ~16V. Unfortunately still getting voltage leakage to the outputs. I thought maybe the new IC was fried from the previous high voltage so I swapped it out for the original. Now I have 17.5V at the rectifier diodes and I get a lot more voltage leaking to outputs. What is interesting is I checked the power transformer wires coming into the board and it is at 16AC and the after the rectifiers it bumps up to 17. Does that make sense?

Re-checked all my work and made sure all the capacitors I replaced were correct. Also re-checked the resistors and all are within spec.

Wasn't sure if I should try putting in the new IC's for the adapter I bought from Mouser. Not too sure if that would fix the problem and I don't want to burn those if the others are toast.

 

[laatsch55]

After rectification and cap smoothing the DC voltages are 1.4 times the input AC voltages, in a standard full wave type thing...

 

[mjstriker]

After rectification and cap smoothing the DC voltages are 1.4 times the input AC voltages, in a standard full wave type thing...

That makes sense then. Thanks

 

[Gepetto]

Worked on the 2000 a little bit today.Added the Zeners to rectifier diodes and it brought down the voltage quite nicely to ~16V. Unfortunately still getting voltage leakage to the outputs. I thought maybe the new IC was fried from the previous high voltage so I swapped it out for the original. Now I have 17.5V at the rectifier diodes and I get a lot more voltage leaking to outputs. What is interesting is I checked the power transformer wires coming into the board and it is at 16AC and the after the rectifiers it bumps up to 17. Does that make sense?Re-checked all my work and made sure all the capacitors I replaced were correct. Also re-checked the resistors and all are within spec. Wasn't sure if I should try putting in the new IC's for the adapter I bought from Mouser. Not too sure if that would fix the problem and I don't want to burn those if the others are toast.

Appears that you did damage the original op amps if you are now getting more supply voltage just by replacing the op amps.

 

[Gepetto]

Worked on the 2000 a little bit today.Added the Zeners to rectifier diodes and it brought down the voltage quite nicely to ~16V. Unfortunately still getting voltage leakage to the outputs. I thought maybe the new IC was fried from the previous high voltage so I swapped it out for the original. Now I have 17.5V at the rectifier diodes and I get a lot more voltage leaking to outputs. What is interesting is I checked the power transformer wires coming into the board and it is at 16AC and the after the rectifiers it bumps up to 17. Does that make sense?

Re-checked all my work and made sure all the capacitors I replaced were correct. Also re-checked the resistors and all are within spec.

Wasn't sure if I should try putting in the new IC's for the adapter I bought from Mouser. Not too sure if that would fix the problem and I don't want to burn those if the others are toast.

what voltage do you measure at the op amp outputs themselves? Have you checked? Pin 3, 4 10 and 12 should be very close to 0 volts with no signal coming in. If not something is wrong.

 

[mjstriker]

what voltage do you measure at the op amp outputs themselves? Have you checked? Pin 3, 4 10 and 12 should be very close to 0 volts with no signal coming in. If not something is wrong.

4 and 12 both have 16V coming off them. Looking like I need to replace the OP AMP

 

[Gepetto]

4 and 12 both have 16V coming off them. Looking like I need to replace the OP AMP

Look at the circuit diagram Mike. Pins 13 and 5 are connected to ground. This forces the op amp to maintain a virtual ground at pins 14 and 6 respectively by virtue of the feedback network from the output pins 12 and 4 respectively.

 

[mjstriker]

Look at the circuit diagram Mike. Pins 13 and 5 are connected to ground. This forces the op amp to maintain a virtual ground at pins 14 and 6 respectively by virtue of the feedback network from the output pins 12 and 4 respectively.

I can see pins 13 and 5 connected to ground by 22k resistors and is also connected to pins 2 and 8 via 100k resistors. I get 0V and both 13 and 5. I get 4mv at 2 and 8 pins. I get roughly 100mv at 14 and 6

 

[Gepetto]

I can see pins 13 and 5 connected to ground by 22k resistors and is also connected to pins 2 and 8 via 100k resistors. I get 0V and both 13 and 5. I get 4mv at 2 and 8 pins. I get roughly 100mv at 14 and 6

And with the equalizer and tone controls switched to the out position you are getting 16V on pin 3 and 12?

100mV at 14 and 6 is definitely broken...other than the op amp, have you been messing with any other components?

 

[mjstriker]

And with the equalizer and tone controls switched to the out position you are getting 16V on pin 3 and 12?

100mV at 14 and 6 is definitely broken...other than the op amp, have you been messing with any other components?

All controls are out. I replace all electrolytics and cleaned pots. Double checked and all caps are oriented correctly. One mistake I did make was I had switched around one of the rotary wheels for the input selector. I flipped it around and that part has been working fine

 

[mjstriker]

Been working on the 400 lately. Attached some pics. Everything is looking good. Installed Q11 and Q12 only and plugged it in to the dim bulb tester. Unfortunately it failed and the bulb stayed lit. Took out the 2 power fuses keeping the line fuse in and I am getting good voltage (~83V) from tranformer. Re-checked everything and all my wiring and board population looks good. Checked a few points and I think the right backboard is grounding to the chasis. Haven't been able to confirm but it looks like one of the solder points is probably touching in the back.

Eventhough I am going to have to tear things apart, it is pretty exciting to be close. Hopefully it's a straightforward fix

 

[laatsch55]

LOVE THE BABB!!!!!

Did you run a straight edge on the standoffs on the backside to check for too long leads?? Do you have continuity between the backplane ground and the collectors or base bus traces??

 

[fitz43]

Eventhough I am going to have to tear things apart, it is pretty exciting to be close. Hopefully it's a straightforward fix

Now there's a B.A.B.B!

 

[fitz43]

Now there's a B.A.B.B!

Geez Lee, we're thinking alike today.