Ok , I got the Sanken transistors in over a week ago but decided to wait for the Toshiba transistors to come first and try those first.
A day or two after the video in the above post was made and with one half the amp with the 470 ohm resistors mimicking the transistors I was able to adjust DC offset however I still had trouble adjusting Bias to the service manuals 2.5 +/- .5 mv as earlier in this thread. There was adjustment now and back then but it stop adjusting at 1.5 mv. I could adjust back down to 0 or into the negative range but it stop at 1.4-1.5 with enough room on the trimpots to go higher but no change.
So I looked at TR 101 and 102 and both were fine however I did find a solder break on one of my repaired traces to one of those TR's . I fixed it and thought that may well be the issue. But still no luck. Just adjustable to 1.5 mv. I checked all the parts surrounding the trimpot on the schematic and all were ok and within specifications.
So I got the Toshibas in the other day , yesterday I spent time removing the originals and doing some trivial testing with my DCA 75. Now I realize this is not a proper curve tracer for power transistors but its what I have that I know is working correctly ( My Tektronix Type 575 Im not 100% sure is working properly and still an learning to use it ) . So the unknown Toshibas measured close to the ones that were in the unit. And I also measured the Sanken's and the curves for those were also similar , and seemed to have a bit higher hFe and higher results than both sets of the Toshiba's .
I also weighed the two sets and each transistor weighed 10 grams , I have read where fakes were less or more. These were spot on the same.
So this evening I installed the Toshibas and fired up the amp. All went well and nothing went wonky. DC adjusted fine but once again still not able to reach 2.5 mv for bias. So I did as before the current mishap adjusted to the 1.4 and then a little past on both sides. I monitored the power draw on my smart wall socket and power draw did not rise as I adjusted past the 1.4mv point. It was about 23 watts on the Revogi smart plug.
So thats all for today. Tomorrow I will clean it up to remove the smudged thermal paste and then try to pas sound and see if those Toshibas are indeed originals .
Unless the knowledge base here thinks I should see why I can't adjust the bias to spec. I do not think a lower bias would hurt but then again what do I know
New unvetted Toshibas on the left, originals as found in unit on the right.
Athanasios
A day or two after the video in the above post was made and with one half the amp with the 470 ohm resistors mimicking the transistors I was able to adjust DC offset however I still had trouble adjusting Bias to the service manuals 2.5 +/- .5 mv as earlier in this thread. There was adjustment now and back then but it stop adjusting at 1.5 mv. I could adjust back down to 0 or into the negative range but it stop at 1.4-1.5 with enough room on the trimpots to go higher but no change.
So I looked at TR 101 and 102 and both were fine however I did find a solder break on one of my repaired traces to one of those TR's . I fixed it and thought that may well be the issue. But still no luck. Just adjustable to 1.5 mv. I checked all the parts surrounding the trimpot on the schematic and all were ok and within specifications.
So I got the Toshibas in the other day , yesterday I spent time removing the originals and doing some trivial testing with my DCA 75. Now I realize this is not a proper curve tracer for power transistors but its what I have that I know is working correctly ( My Tektronix Type 575 Im not 100% sure is working properly and still an learning to use it ) . So the unknown Toshibas measured close to the ones that were in the unit. And I also measured the Sanken's and the curves for those were also similar , and seemed to have a bit higher hFe and higher results than both sets of the Toshiba's .
I also weighed the two sets and each transistor weighed 10 grams , I have read where fakes were less or more. These were spot on the same.
So this evening I installed the Toshibas and fired up the amp. All went well and nothing went wonky. DC adjusted fine but once again still not able to reach 2.5 mv for bias. So I did as before the current mishap adjusted to the 1.4 and then a little past on both sides. I monitored the power draw on my smart wall socket and power draw did not rise as I adjusted past the 1.4mv point. It was about 23 watts on the Revogi smart plug.
So thats all for today. Tomorrow I will clean it up to remove the smudged thermal paste and then try to pas sound and see if those Toshibas are indeed originals .
Unless the knowledge base here thinks I should see why I can't adjust the bias to spec. I do not think a lower bias would hurt but then again what do I know
New unvetted Toshibas on the left, originals as found in unit on the right.
Athanasios
And I believe those Toshibas from china are original as I can not tell any difference IMO sound wise from left to right speaker .
. Just tried them. The physical size is OK, but the pitch is 10 mm (need 20mm).