[Amps] LK 550-ZC

[Dick Green WC1M]

Guess I have a real late one: it has the fan speed temperature sensor. The
stock fan speed is too slow in low-speed mode, so the fan cycles low-high
constantly. And it's like a freight train at high-speed. I increased the RPM
at low-speed so it goes to high speed much less often. That didn't raise the
noise level very much. I also decreased the RPM in high-speed mode, which
reduced the sound considerably, but didn't appreciably affect the cool-down
time to low speed. I used a temperature probe to make sure the tube
temperatures stayed well within spec.

73, Dick WC1M

> -----Original Message-----
> From: Carl [mailto:km1h at jeremy.mv.com]
> Sent: Thursday, March 15, 2012 6:36 PM
> To: Dick Green WC1M; 'Paul Kraemer'; AMPS
> Subject: Re: [Amps] LK 550-ZC
> 
> Amp International was the last name, Denny was selling into the
> commercial market.
> 
> The ZC included the day to day updates to the ZB, and finalized the ALO
> circuit, QSK, and the step-start and fan speed. Real late ones had a fan
> speed temperature sensor.
> 
> Carl
> KM1H
> 
> 
> ----- Original Message -----
> From: "Dick Green WC1M" <wc1m73 at gmail.com>
> To: "'Paul Kraemer'" <elespe at lisco.com>; "AMPS" <amps at contesting.com>
> Sent: Thursday, March 15, 2012 5:12 PM
> Subject: Re: [Amps] LK 550-ZC
> 
> 
> > As far as I know, there was no individual manual for the ZC. I think
> the
> > "400/500 Series" manual was intended to cover all the variations in
> both
> > series. I don't recall exactly what set the ZC apart from other models
> in
> > the 550 series, but I think it was QSK. The BAMA manual has the
> schematic
> > and some instructions for the QSK Board. Is there some part of the
> manual
> > you specifically need?
> >
> > I happen to have a working LK-500ZC sitting unused in the basement. It
> has
> > QSK, but I'm pretty sure it lacks the No-Tune option (it's been a long
> > time
> > since I used that amp.) I don't recall if it has the "new" step-start
> > circuit discussed in the BAMA manual, but I think so. It carries the
> Amp
> > International label, which I believe indicates that it was one of the
> last
> > amps made by Denny before the enterprise went under. The manual that I
> got
> > from the previous owner is almost identical to the BAMA version, but
> > appears
> > to be an earlier edition. Perhaps that means I have it backwards, and
> that
> > the original company was Amp International and the last-gasp company
> was
> > Amp
> > Supply, and that my amp is an earlier model instead of late one. My
> manual
> > does have the pages missing from the BAMA manual (3, 15, 21-24), but
> those
> > pages don't contain any critical information. The BAMA manual has more
> > complete schematics and bills of material.
> >
> > I did a lot of repair work on the amp when I got it. The previous
> owner's
> > wife had thrown something at him during a fight (a chair, I think),
> and
> > the
> > amp got knocked off the desk. All three tube seals were compromised,
> and
> > when the previous owner turned it on, the resulting arc fried the
> plate
> > choke and a number of other components. I also replaced a 40m output
> cap
> > that was actually broken by the blow to the amp. The meter bezels were
> > damaged, too. I fixed all that stuff, added a glitch resistor to
> protect
> > the
> > plate choke from future mishaps, replaced all of the meter calibration
> > resistors (which had either deteriorated or were replaced by a
> previous
> > owner with the wrong values in order to fool the ALO circuit, throwing
> off
> > the meter readings), slightly increased the fan speed at the low
> setting
> > to
> > prevent it cycling into high speed mode so often, and lowered the fan
> > speed
> > in high speed mode so it wouldn't sound like a freight train.
> >
> > 73, Dick WC1M
> >
> >
> >
> >> -----Original Message-----
> >> From: Paul Kraemer [mailto:elespe at lisco.com]
> >> Sent: Thursday, March 15, 2012 2:29 PM
> >> To: AMPS
> >> Subject: [Amps] LK 550-ZC
> >>
> >> Can someone help me find a copy of manual for Amp Supply LK-550 ZC.
> >>
> >> I have the download from BAMA which covers the 550 but not the ZC
> >>
> >> Thanks
> >>
> >> Paul K0UYA
> >
> >
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