Inverted back plates build

[laatsch55]

Coolness Glen!!

 

[laatsch55]

It is Alive

The hardest part was putting in the drivers. I remembered something about magnets so I got out my little pocket magnet pencil It made things much easier but still was a fight
I found that checking the leg alinement in an old base helped a lot
I must have stewed up something with the little inserts as they stuck up from the board. Did I put them in from the wrong side?

View attachment 22489

The threaded 6-32 standoffs that are soldered in the backplanes??? If so, you are not the first to do that...how about a close up of the backplanes??

 

[grapplesaw]

The threaded 6-32 standoffs that are soldered in the backplanes??? If so, you are not the first to do that...how about a close up of the backplanes??

Here is a shot. The threaded standoff's were soldered from the bottom and the little inserts for the drivers were soldered from the top as in attached photo

 

[grapplesaw]

Here is the DC offset at outputs 3mv and .8 mv

Any fine tuning this ??

I will have to redo this one
I just noticed it was set on Ac volts

Well you got me after all Lee!!!

View attachment 22490

I retested with the meters set on DC volts and got unexpected results. Less than .1 MV in each channel. Does this look right seams to low.
I have left out of the input the high pass cap and resistor and wired direct from the RCA plug to the volume controls.

Comments any one?????

 

[laatsch55]

DC offset using the Rev E board with the OPA op-amps are typically .000, to .001 VDC.....ZERO to 1 millivolt...

 

[laatsch55]

I really dig your voltmeters....

 

[laatsch55]

Here is a shot. The threaded standoff's were soldered from the bottom and the little inserts for the drivers were soldered from the top as in attached photo

View attachment 22495

That's correct Glen.....good job too!!

 

[grapplesaw]

Help please. On load test I get wave distortion on bottom half and on both channels area identical. THD is very low and this was at about 1 volts output when this started. The more volts the greater the distortion
I Tried two different source supply for input so suspect something in the power supply bridge rectifier area

Any thoughts

Did I cook one of the small caps on the bridge rectifier???? I think that because it is equal distortion both channels and only one channel fuses installed at a time it has to be supply cap side or main control board. Could bias transistors cause any effect?? I will isolate the DCP board and check bridge rec with meter next I guess

Glen

 

[laatsch55]

One channel fuses at a time?? You mean rail fuses?? Put all 4 in and try it again....

 

[laatsch55]

At ALL frequencies??

 

[grapplesaw]

At ALL frequencies??

I nobly did 1600 hz
Will post results after redoing full range

 

[laatsch55]

Glen, IIRC , there's something weird that happens when all rail fuses are not in and functioning....

 

[grapplesaw]

Glen, IIRC , there's something weird that happens when all rail fuses are not in and functioning....

Ok I put in both set of fuses no change

Here is 26 hz



Here is 20,000 hz



Here is 2,000hz

 

[laatsch55]

Gets worse the lower the frequency......what power output??

 

[grapplesaw]

Glen, IIRC , there's something weird that happens when all rail fuses are not in and functioning....

I bypassed the DCP board
That eliminated that and any concern of the supply lines running between the DCP board and binding post

I all removed all other test leafs from unit

 

[laatsch55]

Amen, I see Joe is here, time for him to chime in...

 

[grapplesaw]

Gets worse the lower the frequency......what power output??

50 mv input wide open volume control and wave Starr's to break up on bottom half of wave at1.7 volts output with 7 of ohm load

The voltage point has increased over time before distortion

Here is a pushed up voltage photo at 2500 hz

 

[grapplesaw]

Amen, I see Joe is here, time for him to chime in...

And the answer is??
Please Joe
Prity please

 

[laatsch55]

Have you swapped in an amp that has tested clean??

 

[grapplesaw]

Have you swapped in an amp that has tested clean??

Ok I will do that now