I always have to wonder if you people can actually hear.
Whenever the older front-end card needed work, we always replaced it with the newer opamp one. The older one sounded grainy and dirty.
Of course we were using them on very revealing 113dB/W compression drivers.
I really have to wonder what you were hearing in the old ones that you liked?
Whenever the older front-end card needed work, we always replaced it with the newer opamp one. The older one sounded grainy and dirty.
Of course we were using them on very revealing 113dB/W compression drivers.
I really have to wonder what you were hearing in the old ones that you liked?
Hi Chris,
I certainly understand this perspective, but rounding up all the hardware, transformer, doing the chassis work takes a lot of time.
This is where I see the savings.
Also, if there are simple mods that provide large improvements then it makes sense to do them, IMO.
No reason there can't be two efforts one for the early design, another for the later OP amp version.
Pete B.
I certainly understand this perspective, but rounding up all the hardware, transformer, doing the chassis work takes a lot of time.
This is where I see the savings.
Also, if there are simple mods that provide large improvements then it makes sense to do them, IMO.
No reason there can't be two efforts one for the early design, another for the later OP amp version.
Pete B.
anatech said:
Hi Pete,
That's what I mean. Use the old transformer and heatsinks and whatever else is useful. Sometimes the design is worth modifying and sometimes you are further ahead with your own design.
I always examine an amp to try to improve it rather than just gitting it. I don't like work that much!
-Chris
That's what I mean. Use the old transformer and heatsinks and whatever else is useful. Sometimes the design is worth modifying and sometimes you are further ahead with your own design.
I always examine an amp to try to improve it rather than just gitting it. I don't like work that much!
-Chris
Banned
Joined 2002
Not an easy task. I believe this is food for designers.
As said earlier, the second diff pair was replaced by BF493. First diff was MAT02 (probably obsolete as well).
BC550 could be an option.
Q5: BD410
Q6: BC337-40
Q7: 2N5416
Q8/9: ASY29 or any other available germanium
Q10: 2N3440
Q11/12: No idea, I still have the original RCA's in there.
MJ150XX perhaps?
/Hugo
As said earlier, the second diff pair was replaced by BF493. First diff was MAT02 (probably obsolete as well).
BC550 could be an option.
Q5: BD410
Q6: BC337-40
Q7: 2N5416
Q8/9: ASY29 or any other available germanium
Q10: 2N3440
Q11/12: No idea, I still have the original RCA's in there.
MJ150XX perhaps?
/Hugo
Banned
Joined 2002
I've just spent some time reading the service bulletins provided at this site: http://home.earthlink.net/~dimlay/id20.html
It can be seen that there were problems with the early PCB 14
design. The "signaltrasistor.pdf" bulletin points out that the 2N5401 transistors failed, these are 150V, and the solution is to
replace them with MPSA93 which are 200V parts. These are listed as full production, by the way, at the Fairchild site:
http://www.fairchildsemi.com/pf/MP/MPSA93.html
It also states that the first diff pair can be any pair of TIS93, GES93, or 2N5172. It turns out that the TIS93 is a higher voltage part with a Vce of 40V. It is also available from Fairchild:
http://www.fairchildsemi.com/sitese...i=sitemap+id&ia=1&text=TIS97&as=1&render=1&w=
Note that the hfe of 250 min is spec'ed at a low collector current of 100 uA.
All of these front end devices will offer better reliability with the design that regulates down the B+ to the front end.
It is mentioned in the outputs.pdf that the TP9054 was simply a remarked Motorola MJ15024 and was used in the PL700II, but not in the early PL700s.
The app note suggests this Motorola part for the laters series II amps, but not for the earlier PL700. The 2SD555 was never used in production but is suggested as a replacement for early PL700.
This is a 200V, 15A, 200W device.
The drivers as stated to be RCA410, and MJ1800, or MJ2741 are listed as replacements. I could not find these numbers in a Motorola data book, but it did list the MJ410 as a substitute for the RCA410. This is a 200V, 5A, 100W, TO3 part.
It also listed the 2N6308 as similar to the MJ1800.
Pete B.
It can be seen that there were problems with the early PCB 14
design. The "signaltrasistor.pdf" bulletin points out that the 2N5401 transistors failed, these are 150V, and the solution is to
replace them with MPSA93 which are 200V parts. These are listed as full production, by the way, at the Fairchild site:
http://www.fairchildsemi.com/pf/MP/MPSA93.html
It also states that the first diff pair can be any pair of TIS93, GES93, or 2N5172. It turns out that the TIS93 is a higher voltage part with a Vce of 40V. It is also available from Fairchild:
http://www.fairchildsemi.com/sitese...i=sitemap+id&ia=1&text=TIS97&as=1&render=1&w=
Note that the hfe of 250 min is spec'ed at a low collector current of 100 uA.
All of these front end devices will offer better reliability with the design that regulates down the B+ to the front end.
It is mentioned in the outputs.pdf that the TP9054 was simply a remarked Motorola MJ15024 and was used in the PL700II, but not in the early PL700s.
The app note suggests this Motorola part for the laters series II amps, but not for the earlier PL700. The 2SD555 was never used in production but is suggested as a replacement for early PL700.
This is a 200V, 15A, 200W device.
The drivers as stated to be RCA410, and MJ1800, or MJ2741 are listed as replacements. I could not find these numbers in a Motorola data book, but it did list the MJ410 as a substitute for the RCA410. This is a 200V, 5A, 100W, TO3 part.
It also listed the 2N6308 as similar to the MJ1800.
Pete B.
Just thought I'd mention that I prefer the pl20 schematic shown here, where the front end supply voltage is regulated down to 20V with a zener: http://members.aol.com/phasetek2/pl20.jpg
Can anyone verify the values of R61, C1, C10, R16, R3, R17, R18, R10, R16? I can't read them.
Pete B.
Can anyone verify the values of R61, C1, C10, R16, R3, R17, R18, R10, R16? I can't read them.
Pete B.
OK, having put more thought into why the service bulletin would state that the 2SD555 should be used in early PL700s and not the Motorola parts we should consider the reason. I found this post with data on the parts:
http://www.diyaudio.com/forums/showthread.php?postid=760025#post760025
The important data, 200V, 10A, 200W, Ccbo=300pF, ft=15 MHz at 200mA, hfe of 40,70,200 min/typ/max at Ic=2 A for the base part. Dash versions of the part offer the following hfe min-max, :
-Q 100-200
-R 60-120
-S 40- 80
all at Ic=2A
It seems that these are fast high beta parts, and I believe that the slower parts might be more prone to oscillations. Just noticed that d3imlay states here that the 2SD555 parts have a tendency to oscillate but that the MJ2119X part do not:
http://www.diyaudio.com/forums/showthread.php?postid=1052148#post1052148
It seems that the design is sensitive to part type and speed. I only just read this by d3imlay and was hoping that the service report would offer a concrete indication as to which part is best, however it seems to contradict d3imlay. I'm back to thinking that stability analysis is needed.
Pete B.
http://www.diyaudio.com/forums/showthread.php?postid=760025#post760025
The important data, 200V, 10A, 200W, Ccbo=300pF, ft=15 MHz at 200mA, hfe of 40,70,200 min/typ/max at Ic=2 A for the base part. Dash versions of the part offer the following hfe min-max, :
-Q 100-200
-R 60-120
-S 40- 80
all at Ic=2A
It seems that these are fast high beta parts, and I believe that the slower parts might be more prone to oscillations. Just noticed that d3imlay states here that the 2SD555 parts have a tendency to oscillate but that the MJ2119X part do not:
http://www.diyaudio.com/forums/showthread.php?postid=1052148#post1052148
It seems that the design is sensitive to part type and speed. I only just read this by d3imlay and was hoping that the service report would offer a concrete indication as to which part is best, however it seems to contradict d3imlay. I'm back to thinking that stability analysis is needed.
Pete B.
PB2 said:
I happen to have an old RCA data book that lists this brief data for the RCA410:
200V, 125W, hfe=30-90 at Ic=1A, ft=2 MHZ typical,
there is no Ic max listed, and it is stated to be in the 2N6510 family.
Several sources list the 2N6510 as a 7A max Ic part, so it seems that the MJ410 is low both on power, and Ic max. The 2N6510 has a lower range of hfe 10-50 and the RCA410 might be selected for high hfe.
The MJ410 does have the higher 30-90 hfe spec.
Seems that a 2N6510 or 2N6306 selected for hfe=30 or better at Ic = 1A would work for the drivers. These seem to be discontinued but there is old stock of them out there.
Pete B.
Hi Pete,
I used to stock 2SD424 and 2SB554 as well as 2SD555 and 2SB600. Wonderful output devices. I can't say that I had any trouble with oscillation with these.
Of course I also stocked the jedec numbers, or ordered them as required.
I would suspect that the layout may have something to do with devices oscillating. Yes, the 2Sx series seemed to be faster with higher gain.
-Chris
I used to stock 2SD424 and 2SB554 as well as 2SD555 and 2SB600. Wonderful output devices. I can't say that I had any trouble with oscillation with these.
Of course I also stocked the jedec numbers, or ordered them as required.
I would suspect that the layout may have something to do with devices oscillating. Yes, the 2Sx series seemed to be faster with higher gain.
-Chris
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.