It was certainly oscillation of ALC amp at 15MHz , whether my unit may have something fault.
Once I reverted mods and found it still oscillate some input range and frequency.
I tried to set ALC control manually with switches on A2 board and confirmed it occurs when ALC amp is 6dB gain.
In frequency setting, I tried experiment then found it relates number of running relays of notch frequency setting, ie, ALC oscillate when input is 777Hz -9 relays are on ,but do not at 888Hz -3 relays.
Thus it may be due to very small stray capacitance.In conclusion, oscillation stops removing A1 C66.I do not see why 100pF is here ,so I put 100ohm in series to it to be snabber.
Once I reverted mods and found it still oscillate some input range and frequency.
I tried to set ALC control manually with switches on A2 board and confirmed it occurs when ALC amp is 6dB gain.
In frequency setting, I tried experiment then found it relates number of running relays of notch frequency setting, ie, ALC oscillate when input is 777Hz -9 relays are on ,but do not at 888Hz -3 relays.
Thus it may be due to very small stray capacitance.In conclusion, oscillation stops removing A1 C66.I do not see why 100pF is here ,so I put 100ohm in series to it to be snabber.
That's great news. Even if its unique to your unit it may help with another.
I could not find a C66 on the A1 board in the schematics I have. Am I looking in the right place?
I noticed that the values around the notch filters are different from generation to generation as well as for the different notch's in the sequence. I'm sure the values on the boards were found by manual substitution when it was designed. And that would mean component tolerance and variations in opamps could cause problems.
I could not find a C66 on the A1 board in the schematics I have. Am I looking in the right place?
I noticed that the values around the notch filters are different from generation to generation as well as for the different notch's in the sequence. I'm sure the values on the boards were found by manual substitution when it was designed. And that would mean component tolerance and variations in opamps could cause problems.
If it's a C unit there are some undocumented parts on the A1 and other boards
I pull my A1 board and look this C66.
No oscillation in my 725C.
Yes, we want mods for the 725D.
Richard, how does that old transistor parameter tester
The Big Orange, do testing wise compaired to Atlas DCA55?
Or what ever the number is? Are you feeling in a loaner mode?
feeling in a rental gear mode?
The reason I ask is that I have about 250 transistors that I need to
go through for all the usual parameters. Have box will travel,
free shipping for you both ways too?
Figured you porobably aren't going to take that along with you
over in the Land of Smiles.
Please advise.
Richard, how does that old transistor parameter tester
The Big Orange, do testing wise compaired to Atlas DCA55?
Or what ever the number is? Are you feeling in a loaner mode?
feeling in a rental gear mode?
The reason I ask is that I have about 250 transistors that I need to
go through for all the usual parameters. Have box will travel,
free shipping for you both ways too?
Figured you porobably aren't going to take that along with you
over in the Land of Smiles.
Please advise.
The Atlas seems like it would be OK for matching BJT. However, it doesnt do well with jFETs at all. Neither the standard nor the PRO version.
You will need something else for jFEts.
What gear are you looking for?
-RNM
Something likethat Quan-Tech, does that work on all these different devices?
Does it also check and meaure the tO66, TO3 outputs, and do the out put device matching.
That or a TEK curve tracer. I wonder if RN could be talked into renting it/them to me for a reasonabley. What do you think would be fair Richard?
I have to ask you, because you are the only one I know that has this stuff.
C"heerys,
It's always fun and games over n Tejas.
The latest for my Shibasoku is I 'm looking for a capacitor.
My scope fell and took some boards with it, in this case
a cap lead was sheared off.
It is the black box cap on the A4 board. Cap C52.
With the following lettering in silver on top:
NQP 2A 2003F
SE 4J
It's value as measured is 202.4nF
D=0,
Q=OL
ESR= 0.08
I'm guessing it is probably a Soshin some type of film.
I can't dig deep enough around to get the lead exposed
and solder in an extension wire to solder onto the board.
Going to be looking.
The latest for my Shibasoku is I 'm looking for a capacitor.
My scope fell and took some boards with it, in this case
a cap lead was sheared off.
It is the black box cap on the A4 board. Cap C52.
With the following lettering in silver on top:
NQP 2A 2003F
SE 4J
It's value as measured is 202.4nF
D=0,
Q=OL
ESR= 0.08
I'm guessing it is probably a Soshin some type of film.
I can't dig deep enough around to get the lead exposed
and solder in an extension wire to solder onto the board.
Going to be looking.
The good news is I dug into the cap to be able to meausre all the
parameters.
I put together a cap (two .1uf) caps that match the Soshin closely. : )
For example, I measured the standard cap paremters the DE 5000
provides, nF, D, Q, & theta, ESR, from 100Hz, 120Hz, 1kHz, 10kHz,
100kHz.
Plugged it in and it works fine from what I can tell. I tried both A & B
on the unbalanced...same meter readings.
I need to go back and find how Demian used the 725D with his FFT or with his
phone FFT or something like that.
parameters.
I put together a cap (two .1uf) caps that match the Soshin closely. : )
For example, I measured the standard cap paremters the DE 5000
provides, nF, D, Q, & theta, ESR, from 100Hz, 120Hz, 1kHz, 10kHz,
100kHz.
Plugged it in and it works fine from what I can tell. I tried both A & B
on the unbalanced...same meter readings.
I need to go back and find how Demian used the 725D with his FFT or with his
phone FFT or something like that.
Had some time to look at this today and this is what I've found.
A lot of work to be done here. It will take a while.
First pic is Richards 725D unmodified.
Second pic is my 725C modified.
Can't justify why the 20kHZ filter on the 725D sends the meter almost to FS.
The 725C raises the noise 1dB
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David,
The levels are about 14 dB different, can that account for the difference?
RNM
62.6 Hz, -86.03 dB
Davada
62.6 Hz, -100.43dB
If so I can do similar with my 727D and the post same.
At least you would have two 725Ds plots.
I'll be able to follow along if you like and point out anything
that is confusing to me which might help others also.
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