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

[sae-7125]

improved ventilation possibility although spacers and longer hardware would be needed for the top


side screws make this position easy, possibly use large diameter washers to help hold the chassis top in place. mounting hardware on top would still be a better idea in regards to child safety testing.

caps are not a permanent addition, just improving air flow for bench testing. taller chassis legs/feet wouldnt be a bad idea. perhaps vibration absorbing options since microphonic tubes can hear anything (sonic, electrical and mechanical noise).

 

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trimming off some of the excess wire that gets compressed under the pcb

 

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electro-picasso anyone? should be close enough to the final build for level-1 testing and some demo room exercise.

 

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closer look at the reinstalled relay and its circuit modz. the factory 47uf electrolytic has been replaced with a pair of 1uf film caps which greatly shortens the rc time constant. ideal click time after system power up might be somewhere around 10 seconds or down to 6 seconds.

in terns of heater/filament health or cathode health and longevity using higher grade glassware might offset any lifespan reduction, assuming there is any measurable injury to the bottles when signal is applied a few seconds after heater is active.

most likely a concern for direct heated triodes only.

 

[sae-7125]

circuit design, might wire this up in a sim to evaluate modz better

the 1 minute or beyond that the factory set was most likely for minimizing power/wake up noise that tube systems naturally produce.

the 3.5s click time right now is a little too short but it will be dialed in eventually. adjusting the 1.2meg resistor upward plus adding a higher value film cap should take care of things nicely vs waiting for what feels like an eternity before the relay clicks after power up. it could be that q4 or q5 are out of spec but its a trivial concern at this point.

another note is circuit discharge rate, you want the relay to de-energize fast as possible when cycling the power button. the relay on this system shorts the output when power is off and for good reason. large dc spike to the power amp when turning off preamp before power amp.

 

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the jj double cap on its side to fit in the chassis with wire extensions. also small chassis ground cap moved to top side of pcb vs under as shown in previous photos.

 

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hot melt glue sufficient for the big, and potentially temporary, low temperature cap. lots of breathing room on deck which will help with air flow and fewer film caps getting melted.

 

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some performance testing before the preamp spends time in the new demo chamber to evaluate overall performance. the next batch of modz will be fine tuning the power supply cap, relay timing, new or nos bottles and maybe some premium output caps.

 

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exterior thermal scan, technically the outer shell is reversed since the vent is normally over the mains txf and power supply caps. its nice that the mounting screw holes line up perfectly to move ventilation somewhere that is always hotter i.e. over the tubes. should improve convection cooling even though the line stage tubes are still covered. heat is being directed away from the power supply electrolytics and allowed to exit quicker.

might be a while before the "round 2" updates are installed, timeline uncertain.

 

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next up is an older bryston 4b power amp

 

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Bryston 4B Power Amplifier, OG Canadian Power!

The Canadian-made Bryston 4B Power Amplifier is a 250 watt per channel powerhouse. The basic design was initially introduced in 1972 and has been a staple for the company since its founding 50 years ago, with some tweaks along the way. The 4B is a modified Class AB amplifier, with a very...

holthill.com

*looks like pro version with XLR inputs

Bryston 4B power amplifier | Stereophile.com

On January 1, 1990, Canadian electronics manufacturer Bryston instituted a remarkable warranty program that covered each of their products for a full 20 years. This warranty includes all audio products ever manufactured and sold under the Bryston name. Besides covering parts and labor costs, the...

www.stereophile.com

*talks about newer 90's 4b with smaller power caps

 

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Bryston 4B Amplifier (Nov. 1985)

*specs and tech write up

Bryston electronics (ad, Oct. 1987)

*brochure product lineup, some photos

 

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taking a look inside the bryston. system is functional, one channel had most of its outputs replaced at some point in time. the other channel looks original, no signs of a recap or extensive circuit changes/repairs/modz.

 

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modular channel removal interesting to see. unfortunately desoldering components requires removing all the output transistors which is messy. i wonder how many amps the sliding pin edge connectors are rated for. definitely going to need contact enhancer to reduce junction resistance for improved output.

 

[Nashou66]

View attachment 3660010
modular channel removal interesting to see. unfortunately desoldering components requires removing all the output transistors which is messy. i wonder how many amps the sliding pin edge connectors are rated for. definitely going to need contact enhancer to reduce junction resistance for improved output.

I use Stabilant22 for that.

What's your preferred contact enhancer?

Nashou

 

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Posthorn | Stabilant 22

https://shop.boeing.com/cpd/bdi_stabilant22%3D33

Stabilant22

cant say that i have bumped into stabilant22/22a although there hasnt been much of a deep dive into contact cleaners and enhancers in my day-to-day activities.

DeoxIT® Gold, Gx Series, GX100L-2DB (Brush) - CAIG

DeoxIT® Gold Gx Series, GX100L Brush Applicator, 100% solution, 7.4 mLExtended Temperature*, approximate, -45 C to +240 C(Applications = 500 +/- brush strokes, 10mm long) Part No. GX100L-2DB (7.4 mL)

caig.com

typically use this in various areas but i am finding deoxit in general tends to fall short on some types of surface corrosion and switch contacts. better off rebuilding the switch which is quite messy or not possible.

the high temp rating, which has an asterisk warning, seems to help signal tube pins oddly enough.

more research is needed to find a somewhat universal contact cleaner/protector/enhancer. zero brand/hype loyalty will be needed as well for a suitable comparison.

 

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Audiogon Discussion Forum

I have been doing some research on the topic of contact enhancers. I've used the Stabilant 22A contact enhancer. I understand other options occur in thi...

forum.audiogon.com

Contact enhancer. A REAL SNAKE OIL. What is your experience with it ?

I want to talk about my experience with the contact enhancer with you. I have test the Furutech Nano Liquid and applied on almost all mechanical connection as a member cdacosta suggest in another thread and I was surprised by the result I obtain using this. The sound is cleaner, faster base...

www.head-fi.org

Contact Enhancers

Do they work? I don't have the tools to measure tiny changes, maybe amir does. Care to test them? Here's someone that might, although he's apparently a vendor, so there has to be a level of suspicion... ----------------- http://ralaudio.com/stabilant-22-contact-enhancer-m-2.html?info=stbtn024...

www.audiosciencereview.com

various links for future reference, maybe it will help me focus on the topic in general.

 

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Top 10 Metal Conductors of Electricity

The following article is a thorough analysis of the top ten metal conductors of electricity. It discusses each metal's electrical conductivity, resistivity, properties, and extensively practical uses in everyday usage.

www.samaterials.com

this should help set a starting point at a molecular level.

 

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Can graphene compete with copper in electrical conductivity?

A pristine, single layer of graphene outperforms copper in electrical conductivity by 70%. How much remains of this in macroscopic films or filaments?

www.bosch.com

materials comparison

Contact Enhancer - Mad Scientist Audio

Your Content Goes Here Your Content Goes Here Graphene Contact Enhancer Graphene Contact Enhancer We are pleased to announce our new Graphene Contact Enhancer (GCE). This can be used on any metal-to-metal contacts, such as RCA plugs and sockets, loudspeaker leads, fuses, and so on. With...

www.madscientist-audio.com

graphene contact enhancer

 

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compact modular channel with 3 interconnected boards plus another edge connector