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Phase Linear 700 WOPL (Early Version Model 700)
- Thread starter Mark Allen
- Start date
6:00 News Part 2....
Left Image: New Jacks were too small for the original PL hole and insulator. So I devised a trick using a piece of cut off resistor lead wrapped around the threaded part of the jack.
Right Image: Rewired input section. The back to back diodes are gone and the PL ground to earth resistor scheme installed. Odd resistor values those are... 2.7 and 56 ohms??? How derived that one? I normally do 10 ohms from signal ground to earth ground.
Seems like I can only ad two images per post.
Yes, the Zobel is on the meter board.... I changed out the caps as they were only 100 volt caps.
Left Image: New Jacks were too small for the original PL hole and insulator. So I devised a trick using a piece of cut off resistor lead wrapped around the threaded part of the jack.
Right Image: Rewired input section. The back to back diodes are gone and the PL ground to earth resistor scheme installed. Odd resistor values those are... 2.7 and 56 ohms??? How derived that one? I normally do 10 ohms from signal ground to earth ground.
Seems like I can only ad two images per post.
Yes, the Zobel is on the meter board.... I changed out the caps as they were only 100 volt caps.
6:00 News Part 3....
Left Image: I replaced all the emitter resistors with 1% tolerance.
Right Image: I noticed the positive regulator seems to be running quite a bit hotter then the negative regulator is. Is this normal? I can't quote any temperature specs yet but I will tomorrow. Positive regulator measures about 15.45 volts and the negative is about 15.12 volts. Offset is still very low down in the mv range.
I also only have 4 outputs in per channel at the moment. I need to go to the parts store tomorrow and pick up some new mica insulators. I can also get ceramic TO-3 insulators but I think I'll save those for when I take it full complimentary.
Mark
Left Image: I replaced all the emitter resistors with 1% tolerance.
Right Image: I noticed the positive regulator seems to be running quite a bit hotter then the negative regulator is. Is this normal? I can't quote any temperature specs yet but I will tomorrow. Positive regulator measures about 15.45 volts and the negative is about 15.12 volts. Offset is still very low down in the mv range.
I also only have 4 outputs in per channel at the moment. I need to go to the parts store tomorrow and pick up some new mica insulators. I can also get ceramic TO-3 insulators but I think I'll save those for when I take it full complimentary.
Mark
Phase 700's with Honeywell VU meters. (Zoebel Network Location)
Phase Linear used a variety of ways to illuminate the Honeywell VU meters used on later 700's. In the case of many of the amps with Honeywell meters, the Zoebel network is on the meter drive board (i.e. PL 7M or PL16A). There were (4) peanut sized bulbs (like the ones used on Phase 400's) used to illuminate the VU meters. The pc board was screwed to the bottom of the VU meters. The bulbs mounted through holes which were drilled out on the bottom of the meters. It appears that the bulbs in your amplifier have been replaced at one time with the same type of bulbs used on 700B's. Phase Linear also used fuse holders glued above and/or below the Honeywell VU meters with fuse style panel lamps to illuminate the meters. In this case, the Zoebel should be mounted on the speaker binding posts.
I would recommend re-locating the Zoebel network in your amplifier to the speaker binding posts.
Earlier Phase 700's used Argonne VU meters which had small bulbs internal to the VU meter. The Argonne VU meters are the best VU meters Phase Linear ever used. I have never seen one fail. The Honeywell's had a high failure rate much like the Midland's used on early 400's.
Ed
Phase Linear used a variety of ways to illuminate the Honeywell VU meters used on later 700's. In the case of many of the amps with Honeywell meters, the Zoebel network is on the meter drive board (i.e. PL 7M or PL16A). There were (4) peanut sized bulbs (like the ones used on Phase 400's) used to illuminate the VU meters. The pc board was screwed to the bottom of the VU meters. The bulbs mounted through holes which were drilled out on the bottom of the meters. It appears that the bulbs in your amplifier have been replaced at one time with the same type of bulbs used on 700B's. Phase Linear also used fuse holders glued above and/or below the Honeywell VU meters with fuse style panel lamps to illuminate the meters. In this case, the Zoebel should be mounted on the speaker binding posts.
I would recommend re-locating the Zoebel network in your amplifier to the speaker binding posts.
Earlier Phase 700's used Argonne VU meters which had small bulbs internal to the VU meter. The Argonne VU meters are the best VU meters Phase Linear ever used. I have never seen one fail. The Honeywell's had a high failure rate much like the Midland's used on early 400's.
Ed
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Agreed and thanks again for the new grounding diagram. I do still have some more work to do in there and tomorrow I'm picking up a piece of 6 gauge copper for the ground buss that's also large enough to mount the bridge on to and then I can eliminate that blue metal divider plate. I also have to weed out two other ground to chassis ground connections where the non polarized caps grounds were soldered to the three point terminal strip in the center of each output stage. The Old 700's had at least three ground loops wired in! I do not want the level pots in there, so bypassing that part. If I can get a hold of two decent stepped attenuators I'll consider putting those back in. But I'm against using pots in general where audio flows through them.
Mark
Agreed and thanks again for the new grounding diagram. I do still have some more work to do in there and tomorrow I'm picking up a piece of 6 gauge copper for the ground buss that's also large enough to mount the bridge on to and then I can eliminate that blue metal divider plate. I also have to weed out two other ground to chassis ground connections where the non polarized caps grounds were soldered to the three point terminal strip in the center of each output stage. The Old 700's had at least three ground loops wired in! I do not want the level pots in there, so bypassing that part. If I can get a hold of two decent stepped attenuators I'll consider putting those back in. But I'm against using pots in general where audio flows through them.
Mark
Listening to the amp.....
I cleaned up the grounding, still have to get a large enough piece of copper for the ground buss... so my ground buss is still as it was from the factory but with no ground loops any more. Input ground also cleaned up. Fed a signal into it and all was well. Went to set the bias and all was not so well. Bias turned all the way down was over 400 mv on the right channel and 450 on the left. The higher of the two settled down to about 438 and so I matched the other channel to that right now. Its a tad high but not awfully so. I'm not sure why this is other than the only bias transistors I could get locally were the NTE devices. I do have a resistor in place of one of the diodes. Perhaps lowering that value or perhaps just jumpering it would bring the bias back in range. Can someone recommend the best step to follow there to fix this?
Positive regulator still seems way to hot to me. If I left my finger on it for more then 4 seconds after shut down I'd have griddle marks. Is this normal? Seems like eventually it will bake the board brown, perhaps a larger sink? That transistor is dropping a lot of DC! The negative regulator is no where near as hot.
How does it sound? Pretty unbelievable compared to the original. Way better than my Krell KSA-50 MK2 and far better than my Aleph 2 Monoblocks. The amp just never runs out of steam, maintains it's huge sound stage and clarity even at high power levels. This amp sounds so good I may leave it as-is except for installing all new MJ21196's, I have the MJ21194's that came in it right now. I will just look for a used 700B to do the full complimentary conversion...
Mark
I cleaned up the grounding, still have to get a large enough piece of copper for the ground buss... so my ground buss is still as it was from the factory but with no ground loops any more. Input ground also cleaned up. Fed a signal into it and all was well. Went to set the bias and all was not so well. Bias turned all the way down was over 400 mv on the right channel and 450 on the left. The higher of the two settled down to about 438 and so I matched the other channel to that right now. Its a tad high but not awfully so. I'm not sure why this is other than the only bias transistors I could get locally were the NTE devices. I do have a resistor in place of one of the diodes. Perhaps lowering that value or perhaps just jumpering it would bring the bias back in range. Can someone recommend the best step to follow there to fix this?
Positive regulator still seems way to hot to me. If I left my finger on it for more then 4 seconds after shut down I'd have griddle marks. Is this normal? Seems like eventually it will bake the board brown, perhaps a larger sink? That transistor is dropping a lot of DC! The negative regulator is no where near as hot.
How does it sound? Pretty unbelievable compared to the original. Way better than my Krell KSA-50 MK2 and far better than my Aleph 2 Monoblocks. The amp just never runs out of steam, maintains it's huge sound stage and clarity even at high power levels. This amp sounds so good I may leave it as-is except for installing all new MJ21196's, I have the MJ21194's that came in it right now. I will just look for a used 700B to do the full complimentary conversion...
Mark
- Joined
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It did have the PLO-171 board.... I can order some 2N5088's... but comparing the two the NTE's have quite a bit higher operating voltage and current 75 volts vs. 30 volts for the 5088. The thermal tracking is actually pretty good too. The amp doesn't run nearly as hot as it used to without the devices mounted to the rear panel...
So whats the big difference between the NTE's and the 2N5088?
By the way... NO one seems to stock the On-Semi. It's either Central Semiconductor or Fairchild.
Mark
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- Joined
- Jan 14, 2011
- Messages
- 74,774
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
ON Semi EOLed their entire TO-92 product line when their packager in Malaysia ceased business on TO-92s They did not want to find an alternative packaging house to continue this piece of their business. Perhaps that will change after their acquisition of Fairchild completes.
Mouser has about 125,000 of the Fairchild 2N5088 in stock. Plenty!!!
Mouser has about 125,000 of the Fairchild 2N5088 in stock. Plenty!!!
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