[Trevor Wilson[_2_]]

"Alan Rutlidge" wrote in message
...

"Trevor Wilson" wrote in message
...

"Alan Rutlidge" wrote in message
...

"Trevor Wilson" wrote in message
...

"Alan Rutlidge" wrote in message
...

So what you are implying is that a transistor tester, capable of
reading current gain and Vbe is beyond the budget or the average
electronics tech and beyond his / her competency to use? Pull the
other one Trevor, it's got bells on it.

**No. That's not what I'm telling you. The problem is acquiring the
sheer number of devices, in order to obtain suitable matches. Not only
that, but Peter matches his large signal devices at 1 Amp. Few techs
bother testing at more than a few ma.

So what's going to happen if one of my output devices fails and there
are no matching spares?

**That is a reasonable concern. That *may* happen one day. You may need
to consider your options at that time. However, right now, there are
plenty of spares available. At my best guess, those spares will likely be
available for the next 20 years or so. Possibly longer.

I guess the whole lot of the output devices would need to be replaced.

**Yep. That is one possibility.

So
the customer bears the cost of the other undamaged devices and the
labour cost associated with that?

**Yep.

Show me the economics in that rationalisation.

**All transistors in the amplifier stages are matched to within 1%
for hFE and Vbe. The resultant number is written on the top of the
output devices.

**Maybe, maybe not. Batch numbers don't tell you much. Peter matches
the devices, based on their MEASURED parameters, not what the
manufacturer may claim.

I wasn't refering to the transistor manufacturer's batch numbers but the
numbers hand written on the top of the devices (presumably by PS or one
of his former employees).

**They're not batch numbers. They're numbers which indicate the hFE and
Vbe matching characteristics of the device. The term 'batch numbers' is
always understood by people in the business to mean the batch number from
the manufacturer. I am sorry for the misunderstanding.

No problems Trevor, no apology required. Perhaps I should have made
myself clearer in the first instance.

So, IOW, the numbers written on the tops of the MJ15024 devices in any one
amplifier module should read the same?

**If not the same, then very close. Within 1%.

Likewise for the MJ15026 devices (except they could bear a different
number as they are a different device). Right?

**MJ15025 and yes.

Trevor Wilson



** Posted from http://www.teranews.com **