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across the bench: an electronic menagerie of diagnostic oddities plus photos and design analysis

bryston 4b - 38.jpg
looking at component space/clearance (right channel), making sure there is enough breathing room for the radial/taller components. after completing the second channel (left) there is a tight fit near the power switch, slight limitation.
 
bryston 4b - 45.jpg
unfortunately the parallel cap closest to the high heat parallel resistors takes the biggest thermal hit regardless how the pcb is mounted in the chassis.

so the heat shield thinking is only partially effective. either way the closest cap is getting cooked, even at system idle, from the inside and outside. film is more robust than electrolytic but there are limits either way.

no win scenario unless major redesign or even more aggressive wattage rating for the closest resistor(s).

direct pcb connection of output sockets probably not helping either when the amp channels are exercised.
 
bryston 4b - 46.jpg
looks like the thermal response needs some adjusting, setting the bias around 2.5mv even though it is unusually twitchy/unstable.
 
bryston 4b - 47.jpg
upgraded the front end wiring (rectifier to power caps) using the previously mentioned 14ga and ditched the stock ~18ga stuff. ideally bumping up the 3+3 south of the power caps might tweak performance but we shall see/hear.

unfortunately the rail still sags even with low to medium output volume. at high output there is around 10v decrease per rail although more than enough reserve to feed the system. each rail at 120v mains are around 82.5v idle, so a total of 165v per channel
 
bryston 4b - 48.jpg
some idle reference numbers including r-ch +rail vs mains level. slowly reaching the end of posting this bryston project, consumed too many pages already.
 
bryston 4b - 49.jpg
testing out in the main chamber, thermals look a little more balanced after adjustments on the bench.

cj pv5 below the bryston and showing off its hot spot as well. plenty of breathing room on the shelf.
 
bryston 4b - 50.jpg
final photo for the bryston 4b even though there are a few updates and enhancements on the to-do list. newer klh speakers getting a workout, sealed cabinets need wattage.
 
mac sl1 - 5.jpg
interesting to note the lack of ground wire for high level input left channel, right channel only for mono input might have something to do with it. photo upper right corner.

mac sl1 - 6.jpg
significant internal brace although the complete lack of acoustic insulation or stuffing of any kind seems odd. vintage mcintosh speakers typically over stuffed arent they? perhaps only the early vintage cabinets.
 
mac sl1 - 7.jpg
screen covering the bass port, its fabric not metal. no indication any kind of stuffing was used in the box unless it was loose sheets easily removed or something.

mac sl1 - 8.jpg
numbers on the subwoofer assembly, two sets of terminals for the wire connections. one on either side of the basket.
 
mac sl1 - 9.jpg
after the fuse holder repair. soldered a piece of wire to hold the questionable electrode design together.

sub seems fully functional but definitely sounds hollow even with frequencies below the box-bark resonance (150-250hz). stuffing the cabinet would definitely help overall performance.
 
sony denon - 1.jpg
quick verification of functionality before they enter the showroom to find a new home

sony denon - 2.jpg
denon pma-737 integrated amp with a versatile phono section. another terrible photo, really need to do something about that one of these days...

sony denon - 3.jpg
sony dvp-s7700 disc player
 

Denon PMA-737 | hifi-wiki.com

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archive.org

Manual: PMA737 SM DENON EN : Free Download, Borrow, and Streaming : Internet Archive

Manual: PMA737 SM DENON EN
archive.org

www.audiosciencereview.com

Sony DVP-S7700 Review (DVD Player)

Hello Everyone, This is a review and detailed measurements of the Sony DVP-S7700, tested here as a CD stereo player and transport. This will be my second review of a DVD player, after the Denon DVD-3910. I will only review it as a CD player and Transport, like I usually perform. So don't...
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Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.
elektrotanya.com
 
visonik d9000 - 1.jpg
an oddball pair of bookshelf speakers with some issues, one midrange partially locking up (aged ferro-fluid or vc alignment?).

visonik d9000 - 2.jpg
spring loaded terminals will need adapters if using banana cables
 
visonik d9000 - 3.jpg
visonik david 9000 made in west germany

Visonik David 9000 | hifi-wiki.com

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David 9000 Speaker-P Visonik; Hamburg, build 1980, 1 pictures |Radiomuseum.org

David 9000 Speaker-P Visonik; Hamburg, build 1980, 1 pictures, Germany, schematics, tubes, semiconductors, Loudspeaker, headphone or earphone
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Sonance'84

Thread 'Calling all Visonik HiFi experts...'

So I picked up a pair of Visonik HiFi 'David 7000' monitors and a 'Sub 1' (passive sub), but will need help sourcing the correct foam for the mid/woofs. Also, one tweeter is blown. I'll have to find someone who can fix it or find a used one. Any tips on who to ask would be great. It's too bad the monitors don't have rubber surrounds like the sub does, which all look very similar to ADS drivers.

This is a cool set and I can't wait to bring it back to life. I'd be interested in any literature on the David 7000 and Sub 1, if anyone has some to share. Being an M&K fanboy, I've heard of...
 
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