Hi All,
It`s been a while since I posted, hope you`ve been keeping well. I`m liking the sites new look.
I`ve been Phase Linear-less for a few years now but I`m back
. I just a acquired a model 700 which looks like it was manufactured yesterday, near mint condition but it`s very sick. The previous owner could only tell me that he purchased it already DOA while working in Riyadh Saudi Arabia back in 1980 and it`s been sitting in a box since. Just to be safe, the first thing that I did was put it on a DBT with all the B+/B- fuses in and took some readings.
With all fuses in, the bulb glowed very brightly but fuses didnt blow. Negligible DC present on both output terminals .250v
With Left channel fuses in and Right channel removed,bulb glows brightly with negligible DC present on both output terminals .250v
With Left channel B+/B- fuses removed,the light bulb dimmed, .250vdc on left terminal but the Right terminal now has 70vdc.
It wasnt until I started opening it up did I realize that someone at some point made an attempt to repair this amp, unsuccessfully. Fortunately the internals seem complete with no evidence of a catastrophic failure but there were a couple of issues, the most obvious being an entire bank of output transistors missing. They dont seem to be OEM transistors either but I could be mistaken.
The other thing that doesn't seem right is, if memory serves me correctly and if this design resembles the 700B, I believe the TO-3 drivers mounted at the bottom of each bank (RCA 410?) were different from the outputs (XPL 909?). Every TO-3 transistor in this amp is a 2N6254, is that even a compatible substitute?
I think I`ll start hunting down some manuals and schematics in the mean time and maybe pull and test all the TO3s and emitter resistors to start.
Seeing it`s such a nice amp, I`d love to resurrect it as I did my 700b with everyones invaluable help that I received here.
Any and all suggestions and recommendations are always most appreciated.
Have a look at some pictures.
It`s been a while since I posted, hope you`ve been keeping well. I`m liking the sites new look.
I`ve been Phase Linear-less for a few years now but I`m back
. I just a acquired a model 700 which looks like it was manufactured yesterday, near mint condition but it`s very sick. The previous owner could only tell me that he purchased it already DOA while working in Riyadh Saudi Arabia back in 1980 and it`s been sitting in a box since. Just to be safe, the first thing that I did was put it on a DBT with all the B+/B- fuses in and took some readings.With all fuses in, the bulb glowed very brightly but fuses didnt blow. Negligible DC present on both output terminals .250v
With Left channel fuses in and Right channel removed,bulb glows brightly with negligible DC present on both output terminals .250v
With Left channel B+/B- fuses removed,the light bulb dimmed, .250vdc on left terminal but the Right terminal now has 70vdc.
It wasnt until I started opening it up did I realize that someone at some point made an attempt to repair this amp, unsuccessfully. Fortunately the internals seem complete with no evidence of a catastrophic failure but there were a couple of issues, the most obvious being an entire bank of output transistors missing. They dont seem to be OEM transistors either but I could be mistaken.
The other thing that doesn't seem right is, if memory serves me correctly and if this design resembles the 700B, I believe the TO-3 drivers mounted at the bottom of each bank (RCA 410?) were different from the outputs (XPL 909?). Every TO-3 transistor in this amp is a 2N6254, is that even a compatible substitute?
I think I`ll start hunting down some manuals and schematics in the mean time and maybe pull and test all the TO3s and emitter resistors to start.
Seeing it`s such a nice amp, I`d love to resurrect it as I did my 700b with everyones invaluable help that I received here.
Any and all suggestions and recommendations are always most appreciated.
Have a look at some pictures.
