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So I am having a hitch in the amplifier part. The right channel bias cannot be set. I already changed the crappy old trimpots for nice multiturn trimmers. There is a diode and the manual says it is a 1.5v zener. The schema on the other hand just shows 2 diodes in series.



Does anyone have a clue as to what this is?

Bert

his067 skrev:It is more than forty years since I passed the T9000 on to a friend, but if memory serves the volume pot has four connector pins. My recollection is that one of these needed to be lifted out of the circuit. But that is as far as I remember ("I was young and happy as the grass was green...." see if you can place that quote. It is from one of my favourite poems)

Let me take a look at this this and report back. I'm too technical for poems in general but my wife tells me it is called Fern Hill (or something like that). She's a teacher ;-).

Bert

notwister skrev:So I am having a hitch in the amplifier part. The right channel bias cannot be set. I already changed the crappy old trimpots for nice multiturn trimmers. There is a diode and the manual says it is a 1.5v zener. The schema on the other hand just shows 2 diodes in series.

T9000 zener.png

Does anyone have a clue as to what this is?

Bert

Nevermind, two diodes in series will of course do the same thing as a 1.5v zener ;-). But that doesn't change the issue. Oddly enough I can see that turning the R*12 while I check the voltage of R29*01 does change the voltage. But when I measure over the resistor I get nothing. I must be blind or something with these mirrored pcb's.

BB

notwister skrev:

his067 skrev:It is more than forty years since I passed the T9000 on to a friend, but if memory serves the volume pot has four connector pins. My recollection is that one of these needed to be lifted out of the circuit. But that is as far as I remember ("I was young and happy as the grass was green...." see if you can place that quote. It is from one of my favourite poems)

Let me take a look at this this and report back. I'm too technical for poems in general but my wife tells me it is called Fern Hill (or something like that). She's a teacher ;-).

Bert

You got it in one. It is a beautiful poem about childhood and mortality....it ends "I was happy, though I sang in my chains like the sea" and though it is a bit gnomic I still like it and think that it encapsulates what happiness is: being aware that you are mortal but also happy with what you are.

Anyway, back to diodes....

Hi all,

got this up and running, one of the resistors was acting up. Replacing it solved the issue. But of course another issue reared it's head. It seems that one of the push switches (12 pole) wasn't working; the speaker selector switch. On analysis it became clear that the switch had broken mechanically. It's old and it's plastic unfortunately. Can't be repaired so must be replaced.

Sadly I don't have this switch. Out of hundreds of switches in my storage of course this one uses some sort of bespoke switch. With very long poles, 12 Poles in total. So i'll need to see if I can source something that will fit (which is bloody likely to be impossible). These switches are hard to find these days. Also, it's a bit unclear what type of switch this actually is. Can't test it because it's broken beyond repairing.

Ah the wonders of vintage hifi ;-).

Bert

Hi,

As I don't have the servicemanual I can't say for sure if this could be a solution.
I'm thinking about replacing the switch with a somewhat simpler type and let it control a relay or possibly two, depending on just how much switching is taking place.
It won't be original, but it will be functional and sometimes the latter is to be prefered imho.

The original switch would that be an ITT Schadow-switch perhaps? I remember that company producing switches which looks like what you describe. You might get lucky searching the web knowing the brandname of the switch.

Best regards and

De beste wensen voor een vrolijk kerstfeest en een gelukkig nieuwjaar.

/Torben

tctla skrev:Hi,

As I don't have the servicemanual I can't say for sure if this could be a solution.
I'm thinking about replacing the switch with a somewhat simpler type and let it control a relay or possibly two, depending on just how much switching is taking place.
It won't be original, but it will be functional and sometimes the latter is to be prefered imho.

The original switch would that be an ITT Schadow-switch perhaps? I remember that company producing switches which looks like what you describe. You might get lucky searching the web knowing the brandname of the switch.

Best regards and

De beste wensen voor een vrolijk kerstfeest en een gelukkig nieuwjaar.

/Torben

Hi Torben,

Thanks for the input but these switches are unmarked and I don't have anything that even comes close to them. You can see the attachment, most likely some old parts they still had. I have many switches but they are all too large in length. The old ones have a very short throw at the end of the switch (where it is held in the metal frame).

I have now ordered some that might fit but their legs are too short. What i'm going to do is grind the legs down (make them thinner). Then I will take an IC holder and remove the legs (I have very long ones). I will push the removed legs of the IC holder onto the legs of the switch and solder them down. That should make them long enough.

Afterwards there still is the problem is actually getting them in. The switches are all held bij a metal bracket and as far as I can tell the entire thing was put in and then the switches were soldered on. It seems to be impossible to remove a single switch. Mine was broken so that was easy, getting a new one in there will be a headache :-(.

De bedste ønsker for en vrolig kerstfest og et lykkeligt nytår.
(That was my best Danish)

Bert