You may consider taking the 2N3055 from the power supply if they show a better HFE figure and send those to the left channel?  Just a thought...

Ok...time to demonstrate my ignorance yet again 😮 I thought that the transistors with the low hfe would cause an imballance on the output and that the ideal would be all transistors within 20% of each other......I'm more than happy to retain the ones that are fitted if the advice is to do so....and it clearly is.

From what I'm hearing here it sounds like the hfe (and therefore the condition of the measured transistors) is good for all but one.....so therefore I will go ahead and replace the black tops and the one offending 37741 (453) sat at hfe 26......

Craig

Look at this.....devastated when I opened up the package from Frede! was well packed too....I suspect the tube it was packed in was squashed by something very heavy, asked Frede if he has any spare lens but thought I would put out an appeal on the forum in case anyone has such a rare thing they no longer have a use for, on a lighter note the panels themselves are tremendous 😁

Sadly moving on......the replacement 2N5320 & 2N5322 also arrived today. The wayward 37741 (423) with the hfe of 26 has now been replaced with a 2N5320 with  hfe of 135...its much higher than the previous incumbent, which when I removed it fully turned out to be a 2N5321 and not a 37741 at all, someone has been here before me, similar hfe to the 2N5320.

Craig,

Just to follow up on your third last post.  I tried to simplify the transistor HFE vocabulary but I'm afraid that I might have introduced the wrong words.  The transistor HFE is the current amplification coefficient.  When used alone, a low coefficient is not really a problem but when used in a multi-stage configuration, bad things can happen because the current is not high enough to drive the following transistor.  I know for sure that an underpowered transistor will introduce distortion but might also cause other undesirable behaviour, which I’m not knowledgeable enough to explain.

For the 2N5321, it might be a very close cousin to the 2N5320.  Check on All Transistors and compare the data.  It should be very similar with better specs but not under.

I have a used facia here I can send over to you.  PM me for this

Craig wrote:

Look at this.....devastated when I opened up the package from Frede! was well packed too....I suspect the tube it was packed in was squashed by something very heavy, asked Frede if he has any spare lens but thought I would put out an appeal on the forum in case anyone has such a rare thing they no longer have a use for, on a lighter note the panels themselves are tremendous 😁

I am sure Frede will come up with something, when I see things like this I get so angry, had it myself a couple of times, ignorant package handlers, here in Mexico I never use Mexpost, they brake it, steal it or it never arrives. I am following with great interest Craig, so keep them coming

chartz wrote:

Hi,

Other than that, excellent work Craig, but I think replacing transistors just because of a bad HFE is a bit overdoing it 😕

Jacques,

By no means I want argue with something so subjective but I think the following thread is interesting.  I had myself a situation with a Philips amp where the DC offset was huge and had to replace the differential transistors to match them.  That alone fixed the issue.

https://audiokarma.org/forums/index.php?threads/hfe-matching-on-transistor-subs-important-for-comp-pairs.757654/

I’ve never had the problem myself to tell the truth but I guess it all depends on the configuration.

Thanks for the link 😀

Moving on.....Frede is posting me a replacement lens, bless him...such a gentleman, I will glue it into place when it arrives. Meanwhile I have replaced the pre-amp blacktop suspect devices...