Re: 6SN7 amp initial report


"jh" <jh@xxxxxx> wrote in message news:gmtqs7$m1k$1@xxxxxxxxxxxxxxxxxxxxxx
Phil S. schrieb:
"jh" <jh@xxxxxx> wrote in message
news:gmmah0$7gf$1@xxxxxxxxxxxxxxxxxxxxxx
Hi Phil,

great....
Yes, feels good to get any sort of result that works. This, as you know,
is a true Franken-amp.

Just a few /very little) comments
AFAIK the C12R has a lousy efficiency, the weber surely does not. If
it's a real Blue Alnico clone, then it's supposed to be a very loud
speaker. Might be th best result for "headroom"

OK, I will try the Weber next. Yes, AFAIK, it is Weber's clone of the
bulldog, but no, this one is ceramic. The Alnico is rather expensive.

With the intermittent 6SN7, if pressing the glass in to the base helps,
you might try to carefully resolder the pins. I've revived more than one
tube...
Yes, pressing glass from the top makes it work. I don't understand
what's involved here. I need to remove the base? How is that done
without breaking it?

Hi Phil
I'd simply try to reflow the tube pins. If it works - ok, if not - nothing
lost. The pins a re just small tubes with the wires coming from the base
sticking through. If you've got a cold solder joint there, it will fix it,
if the wire is broken at the base, it won't and you've got a nice tube for
display....

Not sure when I'll get to it, but, now that I am thinking about it, filament
voltage readings were a bit off on that tube and it seemed to light up when
I pushed down on the glass. Assuming it is the filaments, there are only
two pins to fool with. I'll may need another can of gas for the butane
soldering iron, which is capable of more heat than the Weller electric I use
most of the time. I'll see if the electric will do the job. Funny thing,
the gas ran out on this last build. I was using both irons together to melt
the main ground lug to the chassis and it worked much better than I
expected.


With the distortion analysis (tubes vs transformers), i guess it's
really time for a scope now. My first scope (that i really miss) was an
old Tek 561? (i'm not at home to look what it exactly was) Two trace,
differential input, max 20MHz. It served me really well for years, Real
big mother, enough heat to warm a room, but great low level results,
perfect for audio work. Really tough regarding abuse - applying 550V DC
while in mV settings etc. I only realized what i lost, when I had the
replacement. Also a tek, but a fairly recent one (2225 or something like
that).
I bet they are dirt cheap, because they are much too slow for digital
analysis. I bought mine in 93 for 120DM then (~60$) it was from an old
university stock.

The language of scopes is confusing to me. This small explanation is
helpful. You're saying I can get the kind that no one wants anymore. I
started to watch auctions on eBay to see how the bids end. As for
brands, you and Steve Cowell like Tek.

I've had/have two teks and have tried one cheap "sino all bells and
whistle" scope for at least 15mins. REAL shitty flickery display,
unstable, it just did not feel right. Sent it back immediately.
Fortunately the TEK arrived from an ebay buy at the same time.

I know, that Steve advises against old tube scopes.
He was very clear about it. The problem is that it will sustain serious
damage in shipping. He didn't seem to have serious objections other than
the ususal, like excessive heat, tube maintenance, etc.

I for myself have been a real happy camper with the (partly tubed) 561A.
Especially the 3A3 diff amp is something i clearly miss. I know, that i'll
recreate/reuse that plugin someday.
I never had any problems with the scope, until it simply refused to work.
OK the guy i bought it from was xactly this grumpy old man with a basement
full of TVs, VCRs and what not to fix and he told me that it was in
perfect working order.
Beeing partly tube it's not one of those colossus scopes; it's about 2x
the size of my TEK 2225

BTW the first and only probe that really failed her *was* the tek probe
that came with the 2225. It also had that fixed ground wire which is
always where don't want it to have.
My other probes *are* an assortment of cheapo probes ranging from
1:1/1:10, 1:10, 1:100. Never had real problems, other than a hook.

just my 02cts.

regards

Jochen

What else is OK? HP? BK? I thought it
would be nice to get a smaller "desktop" model. What's up with probes?
They seem expensive.

regards

Jochen

Meanwhile, we are having an unseasonably warm day today, in the 60's
(15C) and it will be calling me away from the workbench, which is in the
basement.

Phil

I downloaded a 64 page book from Tektronix, "XYZs of Oscilloscopes". A bit
dense, but appears to be what one needs to know and then some. I'm in the
midst of wading through it while I am watching eBay. I've learned to watch
before bidding. There is always another good deal for someone who can be
patient.

Phil


.

Relevant Pages

  • Re: 6SN7 amp initial report
    ... Phil S. schrieb: ... I'd simply try to reflow the tube pins. ... My first scope was an old Tek 561? ... Also a tek, but a fairly recent one. ...
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  • Re: 6SN7 amp initial report
    ... I'd simply try to reflow the tube pins. ... really time for a scope now. ... Also a tek, but a fairly recent one (2225 or something like ... BTW the first and only probe that really failed her *was* the tek probe ...
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