Strauss Polka Head - Schematic Analysis & Starting Work

After tracing out the schematic, I come up with a game-plan and start work to make this one reliable. In the next episode, we'll have a listen, then go to the customer with some suggestions on voicing to make it a more inspiring and versatile amp.

Equipment:

Soldering:
Pace MBT station w/SX100 & PS-90 handpieces
Hakko 474 w/815 handpiece
Hakko 936 w/907 handpiece
Hakko FX-888D w/FX-8801 handpiece
Quick 861DW hot air station
BOFA fume extraction unit
Loctite Multicore solder (C511 / 362)

Test Equipment:
Fluke 11, 175, 177 & 179 handheld DMM's
Tektronix 2236 analog oscilloscope
Rigol DS-1054z digital oscilloscope
BK Precision 4017A sweep / function generator
BWD 160a function generator
HP 6236B triple output DC power supply
Kyoritsu 3132A insulation / continuity tester

Video equipment:
Overhead cam: Panasonic HC-V785 w/Audio Technica AT9946CM mic
Handheld cam: Panasonic DC-G85 w/Olympus M.Zuiko Pro 12-40mm f/2.8
On location cam: Panasonic DC-GH5s w/Panasonic-Leica 9mm f/1.7 & 12-60mm f/2.8
Capture card: Magewell HDMI USB
Editing: Adobe Premiere Elements

Hand Tools:
Wiha, Felo, Stanley screwdrivers
CK & Engineer cutters / pliers
RS Pro wire strippers
Sidchrome & Gear Wrench spanners, sockets & shifters
Veritas planes & chisels

Materials / Consumables:
JJ's / TAD electron valves
Elixir / Ernie Ball / D'Addario / Rotosound strings
Electrolube & DeoxIT cleaners, lubricants & chemicals.

[grandudetonesnob]

I'm enjoying the deep dive into the circuitry rabbit hole on these old curiosities.

[johnpierson]

I liked how you walked through the inspection, cleanup, rework, schematic and analysis. BTW, your hand drawn schematic skills are not shabby, to say the least.

[scottwilcox]

Brad really enjoyed going through the schematic great video much appreciated 👍

[acousticfix]

Awesome work Brad. I've been sporadically rescuing of it's bigger brothers, Polka 200 (4 x KT88s), for a long time. The O/P PCB was so badly burnt so I completely rebuilt it on a bakelite board with tag strips. You have given me the inspiration to finish it off. My current hurdle is finding pots with long collars. I'll pass on a source when I find it. Expect that to be USA for some of those values. I'm also looking at the tone stack and whatever else is making it dull. So.... really interested in what you have in mind. Looking forward to part 3 mate.

[Rico_G]

Figures! First video where I'm on-time and it's *not* a live stream.

[socallars]

Brad, you deleted the livestream for this amp as I was watching it! I love those, they are the perfect thing to play on my shop laptop while I'm working on something. Usually I just listen and will only put eyes on the screen when I hear something interesting in a technical sense. Oh well, it's your channel & content, I thoroughly respect your right to operate it as you see fit.

[johnwilliamson]

Rather than 100p caps of 10 to 15p to stop rf on 12au7 input is more the norm . Must agree 100p is over used in that amp interesting video .

[edwardhannigan]

Top Vid Brad..Great walk thru and schematic info..Love it..Ed..uk..😀

[tedmich]

hmm maybe a custom Polka/Panther dual channel? Great video, as usual!

[zulufrog]

The traces on the power board are BEEFY!

[goodun]

Its still not clear to me if the 6CA7 and EL34 are indeed the "same" because Philips held the pentode patent, which most American tube/ valve manufacturers didn't want to pay; which is how and why "beam power tubes" were developed: as an end-run around the Philips patent. Has anybody here ever taken apart a 6CA7 to see if it has a suppressor grid like a true EL34 pentode does?