Scott LK48B 7189 PP integrated amplifier.

[MikeS]

Aquired locally off Craigslist.

This is the kit version of the 222C or 222D or some such. This was pretty much a family piece that I bought from the Nephew of the Uncle who built the kit.

It came with the original color instruction manual and operating manual, dated 1963.
The Uncle must have ordered a Walnut case to go with the kit. The wood cases were a extra option.
While it was a little rough looking, I carefully sanded it out. It should look WAY better now with a couple coats of boiled linseed oil.

The amp is in pretty good shape cosmetically. It was rather dirty, and cleaned up pretty easy. There is some slight loss of silk screening on the faceplate.

All the tubes are original. Mullard 7189's, with a Mullard 5AR4/GZ34. Telefunken 12AX7's, and Telefunken 6GH8's. The tubes seem to test strong in a tube tester, which isn't saying much.
The Mullard 5AR4/GZ34 is a rather strong rectifier tube. I have two of them now, and they just bury the meter on my transconductance tester.

The Uncle wired the kit pretty good, I think. I've got some funds to order parts, as it needs the selenium rectifier bridge replaced for a modern diode bridge. And the usual things that a 46 year old tube amp needs........coupling caps, out of spec R's, maybe some de-coupling, filter, and bypass caps.

I like the size of the Scott's output iron. I'll be able to have decent bass with a 6BQ5/7189 PP tube amp.

Mike

[MikeS]

I pinched these images from a eBay listing, to show how mine looks.
The unit pictured, is a bit cleaner than mine. Mine's about the same, but with some silk-screen loss.

I have mine partially torn down and waiting for parts. (coupling caps, resistors)

I've straightened and rerouted some wiring to conform more to the instruction manual, and have replaced the selenium rectifier bridge for a radio shack 8 amp 400 volt silicon version.

Someone (nephew?) sprayed some nasty greasy yellowish white shit in all the potentiometers, and switches. The stuff was loaded in the pots/switches, all running out of them and such.

I had to carefully unwire each pot, and then soak them in isopropyl alcohol for many hours, spraying them with compressed air while soaking. Also scrubbing periodically with a toothbrush.
When the pots were finally cleaned off and dry, I went ahead and sprayed them with De-oxit. The switches I cleaned/scrubbed with alcohol the best I could, and then sprayed with De-oxit.

It was no fun to do, but I couldn't deal with that grease all loaded up in those pots. I dunno if it was a conductive type of grease or not, but it doesn't matter now.

I disconnected all the leads to each aluminum multicapacitor can, and then connected a tube DC power supply to each section, (or sections) of each cap can. Then ramping up the voltage on the power supply, monitoring the current meter.
They all seem to reform rather easily up to 400 volts DC. The current meter never moved up over 5 milliamps when quickly ramped up in voltage.

I think I might have lucked out, but the only way to know is to check for ripple on the bench or listen to it.

This is the first kit amp I've aquired where it was constructed well enough to just do some general freshening up and not end up tearing it all apart.

[MikeS]

Finished...pretty much. I'm keeping this one.


http://img710.imageshack.us/img710/7397/003wt.jpg

[95Honda]

Cool.

First time I have been on here in a few months, lol!

[MikeS]

The main power supply cap went tits up...constant 120Hz hum over everything.

I'll buy another multisectional capacitor and some 6GH8/6U8 tubes. One has static noise.

This integrated 6BQ5/7189 PP amplifier is a keeper. It meshes right up with my Klipsch Cornwalls like a old pair of favorite socks. Amazing bass for a 7189 push-pull amplifier with plenty of power.

[MikeS]

I bought a CE multisectional electrolytic for the B+ and screens, and a cheaper JJ multisectional for the pre-amp and phono section.

I also bought some RCA 6GH8A tubes for cheap, just to get things going.

No more 120Hz hum...

A powerful tube amp (integrated) I can actually play thrash metal on without earwire. Thanks to the tone pots and loudness switch.

Good sound...