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across the bench [season-2] the electron strikes back

cj pv10a - 28.jpg
around 37w at 120v

with 59v across the 2.2k there will be 22v across the back half of the crcrc which will be 375v feeding the transistor filter/regulator. not to mention lower magnitude of ripple to be filtered. the 18.2k could be bumped up to 22k or maybe as high as 33k for more aggressive b+ filtering but that will also increase heat generated. a different component was selected to replace the mje340 and its poorly designed factory heat sink.
 
cj pv10a - 29.jpg
a few hot spots, need to take a closer look.

cj pv10a - 30.jpg
inspecting the lift kit. also note the larger filter cap for the 12v regulator circuit (6800uf vs 4700uf factory). the cap is also shifted away from the diode rectifier hot spot.
 
cj pv10a - t7.jpeg
the precision resistors near the line stage bottles should be on the high wattage upgrade list. also interesting to see how hot the reed relays get just idling, room for thermal improvement perhaps.

cj pv10a - t8.jpeg
might be able to drop that temp down to 122f/50c depending on latch voltage spec, need to find a data sheet.
 
cj pv10a - t9.jpeg
560k with the different color mid section near the 10 zeners

cj pv10a - t10.jpeg
the revised heat sink using a different transistor, not another mje340. with a pv5 the heat sink hits 200f and beyond (unmodified). no idea how bad the pv10 might get since this is the first of that model number to go across the bench.

using my hand to isolate the thermal measurement since the sink temp is so low, oh the horror of being cool.
 
cj pv10a - 31.jpg
using the darlington to replace the mje340 and mpsu10, wire jumper used across q2 base and emitter.

cj pv10a - 32.jpg
selector switch has a few spots of corrosion, this preamp must have spent time in a high humidity area perhaps a basement.
 
cj pv10a - 34.jpg
top side looks clean now

system went from x3 electrolytics down to x2 so far. i wonder just how high the heater/filament ground cap needs to be. if a 10uf film would be adequate instead of 22uf/50v. could also design a daughter card module for the 4700uf heater cap and do a low level crcrc plus a darlington filter (full film mod). should run a sim to evaluate the high current vs rc filter effect.

*interesting info about undocumented variations, the usual cj methodology.
 
cj pv10a - 35.jpg
changed the location since 3 of 4 are in attendance

that should do it for the pv10a, owner should consider shopping for less microphonic tubes especially in the line stage area.
 
Screenshot 2026-09-03 at 18-59-08 DIY Audiokarma Home Audio Stereo Discussion Forums.png
www.audiokarma.org/forums/threads/heathkit-w-5m-renovations-boondoggle-edition-quantum-vacuum-deep-dive.1108582/

heathkit w-5m project and analysis has reached a partial conclusion, amp 1 of 2 complete with v1.0 renovation. a long story / picture book of the design and history of a 1955 foundation piece of audio gear. more than a few options available when adjusting the system for high longevity.

since the picture book is about 90% complete it should be easy to digest for those in a hurry vs waiting for an active project to be completed. every viewer/person/bot/interstellar-hacker is different on the world wide web of digital schtuff.
 
lsa hyper - 2.jpg
nice that the side panels can be removed without too much difficulty. perhaps potential modz space to be utilized.

lsa hyper - 3.jpg
fairly simple boards and wiring, nothing messy nor starving for extra space.
 
lsa hyper - 4.jpg
a few factory caps under the board. odd that the electrolytics hugging the tube sockets didnt get the same treatment.

lsa hyper - 5.jpg
should look into how many electrolytics can be converted to film depending on capacitance.
 
lsa hyper - 6.jpg
pcb version and year, also nice photo example of tube vs capacitors

lsa hyper - 7.jpg
it is interesting to note that when the system is powered up and active, regardless of signal, there is a high pitch scream/whine/noise from somewhere on the board. might be one of the smt/smd inductors squawking at a modulated frequency or something.

that would explain the mostly solid top plate chassis design vs the ventilated version shown in the review link posted earlier.
 
lsa hyper - 8.jpg
power brick for the preamp, familiar brand is nice

lsa s100 - 1.jpg
preamp and the next item which needed some diagnostics, new in box bookshelf speakers
 
Screenshot 2026-09-14 at 04-01-42 LSA Speakers Underwood HiFi.png
www.underwoodhifi.com/products/lsa-speakers

**site banner/popup**, walter's health not so good these days, schifter is recovering from a recent stroke.

verafiaudiollc.com/pages/about-us

on a somewhat sour note, i seem to have bumped into some av123 (2010) drama involving a grand jury situation.

in other news, ribbon tweeter + passive radiator = enjoyable experience. some of us tend to prefer this type of highs and lows design solution. the new-in-box LSA Statement 100 issue was not a pleasant surprise though.
 
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