Send me the links for any used scopes that you're interested in. The most important things...
Only consider scopes that have locked waveforms displayed in a well lit room and/or a warranty. Locked waveforms in good lighting likely means that the scope is in good working condition and the CRT is still able to produce an intense trace. A warranty is good but shipping is expensive, especially if you have to send it back (the seller isn't likely to refund shipping). I'd prefer proof that it works (locked display) over a scope that's not powered up but has a warranty.
Only consider scopes that have locked waveforms displayed in a well lit room and/or a warranty. Locked waveforms in good lighting likely means that the scope is in good working condition and the CRT is still able to produce an intense trace. A warranty is good but shipping is expensive, especially if you have to send it back (the seller isn't likely to refund shipping). I'd prefer proof that it works (locked display) over a scope that's not powered up but has a warranty.
Okay just got the three IC chips (4080,3525 and 4424) and carefully swapped them out. I will test it today and hopefuly that got rid of my problem.
Oh before testing it, I also found out two small caps that may had leaked (either one leaked a lot, or two of them leaked). They where right next to the 3525 chip and the other on by the 4424 chip. Will have to look if their traces are with the IC chips, maybe that was my problem. Either way I will remove them and replace them since I also order those two caps.
Oh before testing it, I also found out two small caps that may had leaked (either one leaked a lot, or two of them leaked). They where right next to the 3525 chip and the other on by the 4424 chip. Will have to look if their traces are with the IC chips, maybe that was my problem. Either way I will remove them and replace them since I also order those two caps.
Here are the readings for the 4080.
1)35.64
2)13.24
3).164
4)0
5)6.62
6)6.08
7)6.1
8)5.2
9)5.2
10)35.68
11)28.93
12)23.34
13)6.24
14)0
15)13.24
16)13.24
17)0
18)6.22
19)23.38
20)29
Here are the 3525A readings.
1)5.17
2)5.17
3).015
4).111
5)2.05
6)3.83
7)2.05
8)4.96
9)5.17
10)12.97
11).046
12)12.97
13)0
14).042
15).028
16).36
Here are the 4424.
1)0
2).046
3)0
4).043
5)0
6).040
7)12.97
8).036
All these reading where done with no input signal or speaker load.
I also notice that on pin #7 on the 4080 did not have any triangular waves and I had to set the volt/div on my scope to 1v to see round waves (two minor divisions on the scope).
1)35.64
2)13.24
3).164
4)0
5)6.62
6)6.08
7)6.1
8)5.2
9)5.2
10)35.68
11)28.93
12)23.34
13)6.24
14)0
15)13.24
16)13.24
17)0
18)6.22
19)23.38
20)29
Here are the 3525A readings.
1)5.17
2)5.17
3).015
4).111
5)2.05
6)3.83
7)2.05
8)4.96
9)5.17
10)12.97
11).046
12)12.97
13)0
14).042
15).028
16).36
Here are the 4424.
1)0
2).046
3)0
4).043
5)0
6).040
7)12.97
8).036
All these reading where done with no input signal or speaker load.
I also notice that on pin #7 on the 4080 did not have any triangular waves and I had to set the volt/div on my scope to 1v to see round waves (two minor divisions on the scope).
When the amp distorts, how close to the rail voltage is the top of the sine wave?
**Let me make sure I understand what your asking, your telling me to check the waveform on the rail voltage? The amplifier only distorts on sinewaves signal and at a certain amount of vAc on the speaker terminals. Like around 22vac on my speaker terminals is the max any higher and thats when it starts to distort real bad. It also starts to squeel (a high pitch noise, 20khz maybe) when it starts to distort can't exactly pin point where the squeels come from but its somewhere on the board not the speaker outputs.
Did you replace the outputs in this amp? If so, did you use the IRF3710Z
**I have not replace any outputs, I only replaced all three IC chips that were on a IC socket (4080i, SG3525A and the 4424ZN). Also replaced three electrolytic capacitors (one was the NP by the RCA's, and the other two where by the IC 3525A and the 4424ZN chips. All caps where replaced with same values and type caps,
**Let me make sure I understand what your asking, your telling me to check the waveform on the rail voltage? The amplifier only distorts on sinewaves signal and at a certain amount of vAc on the speaker terminals. Like around 22vac on my speaker terminals is the max any higher and thats when it starts to distort real bad. It also starts to squeel (a high pitch noise, 20khz maybe) when it starts to distort can't exactly pin point where the squeels come from but its somewhere on the board not the speaker outputs.
Did you replace the outputs in this amp? If so, did you use the IRF3710Z
**I have not replace any outputs, I only replaced all three IC chips that were on a IC socket (4080i, SG3525A and the 4424ZN). Also replaced three electrolytic capacitors (one was the NP by the RCA's, and the other two where by the IC 3525A and the 4424ZN chips. All caps where replaced with same values and type caps,
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Set the scope to:
DC coupling
10v/div
2ms
set the scope to display both traces
align the trace to the reference line
place both probes on the rail and confirm that both traces deflect to the same point
place one on the rail and the other on the output terminal
Does each output swing to within a couple of volts of ground and the rail voltage?
Have the output transistors been replaced previously (by someone else)?
DC coupling
10v/div
2ms
set the scope to display both traces
align the trace to the reference line
place both probes on the rail and confirm that both traces deflect to the same point
place one on the rail and the other on the output terminal
Does each output swing to within a couple of volts of ground and the rail voltage?
Have the output transistors been replaced previously (by someone else)?
I'll do the scope test today and post results ASAP. As far as for the output transistors being replaced..... I doubt it, because they look like factory solder joints.
As for the scope tests/readings, should the scope's ground be at RCA's ground or the power's ground? I have plenty of probes so i can use both channels on my Tek 465. Sorry for sounding so dumb but I rather sound stupid then do stupid (ask and confirm before messing anything up, lol)
Thanks.
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