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

[sae-7125]

coming up next will be the cary SLP-98 preamp plus some thermals and mains measurements.


the cute little tube preamp sitting atop a rather large console. just need a pair of smallish tube mono's above each speaker to complete the ensemble.


the usual paperwork and handling instructions. how to feed and care for your tube preamp.

 

[sae-7125]

a few beauty shots and then on to the technical stuff.


i wonder how hard it would be to swap in the black face plate for a high contrast look.


lots of ins and out except for one major deficit, no phono module installed. a separate phono device will be needed which increases shopping potential.


and the rather larger power supply/brick with detachable umbilical.

SLP-98 Preamplifier with Phono Stage (SLP-98L & SLP-98P) | Cary Audio

caryaudio.com

SLP-98 & CAD-120S MkII Package

A tube lover’s dream. As a full tube preamplifier and amplifier combination, this pairing is for those who appreciate the full glory of tubes. The SLP-98 preamplifier has been our mid-level preamplifier for many years. For decades audiophiles have clamored over the natural sonic texture of this...

carydirect.com

Cary SLP 98 - Ultimate Package

This retube kit for the Cary SLP 98 tube preamp consists of the very best tubes we have to offer.

www.thetubestore.com

Upgrades and Modifications | Cary Audio

caryaudio.com

 

[sae-7125]

closer look at the cary power supply, under the hood.


the dynamic duo, although one chassis is in "sport naked" mode for those familiar with motorcycles.


a closer look at the magic hidden within.


120w of dim bulb feeding the supply with preamp active/idle. minimal wattage reduction vs full mains.

*dim bulb fixture received another design rev, might post the photos in the near future. current photo is now an outdated design.

 

[Celadon]

That certainly is a big chunk of iron they used in that PS.
Both my Aragon products, (Aurum and 47K) use separate PS (Ingot and IPS), and of course are SS; but nothing like the size of that xformer! In fact it seems to be Aragon's weak spot.

Now that you mention your new DB tester Rev -- of course we want to see

No coffee yet...
This morning it's Mushroom coffee ---with a really awesome blend, Lions Mane, Shitake, Reishi, Cordyceps, Chaga, and Turkeytail...
You are what you eat -- looks like I'm a toadstool.

That is so wierd that people drop off things for repair-- and then 1-2 years, and some disappearing altogether, of course lots of time life gets in the way-- but...

My best to you, Here's to another productive day, always a great journey through the menagerie; one never knows what we shall find.

Celadon

 

[sae-7125]

This morning it's Mushroom coffee ---with a really awesome blend, Lions Mane, Shitake, Reishi, Cordyceps, Chaga, and Turkeytail...

mushrooms for the win, especially on pizza although some might question my enjoyment of fresh pineapple & mushroom atop a quality flavorful pizza. and then wash it down with a satisfying flavor and texture fruit smoothie (non-gmo).

Product Categories - Bolthouse Farms

Carrots, smoothies, juices and dressings to be reckoned with.

www.bolthouse.com

*nicely fortified flavor "blue goodness" with vitamins and minerals.

something i havent tried yet, mushroom jerky.

Pan's Mushroom Jerky - All Products

Browse our full selection of mushroom jerky: Original, Zesty Thai, Salt & Pepper and Applewood BBQ. Try them all with a Variety Pack! With a delicious umami taste and satisfying texture, Pan’s Mushroom Jerky originates from a decades-old family recipe that’s been updated with new flavors and...

www.mushroomjerky.com

although i am not a big fan of chia seeds or anything soy, sibo/leaky gut is a rather undesirable affliction. the same can be said for runaway inflammation and the joys of arthritis.

for those not familiar with lectins, which can/will damage a digestive tract, dr gundry the author of "the plant paradox" might be a good place to start.

Health Dangers of Lectins - Gundry Health - Dr. Gundry

Lectin dangers in food: disrupts cell communication, increases inflammation, and leads to digestive problems, weight gain, autoimmune diseases. Go lectin-free.

gundryhealth.com

i shouldnt go too far down the health diagnostics/troubleshooting rabbit hole since it could be viewed as "medical" advise or something. i could go on about how vitamin d3 isnt a vitamin (its a hormone) and how rats need d2 and humans need d3. plus the need for quality sleep, but nobody wants to hear about that especially on an audio forum that has its own metric of therapeutic modality. listening to music IS therapeutic.

youtube.com/watch?v=jWe-feh7Twg
*stasha gominak, d3 + sleep + neurology (no more cpap).

youtube.com/watch?v=NBo9_LpXp90
*bruce lipton, epigenetic signal transduction.

youtube.com/watch?v=kp1bZEUgqVI
*scishow, epigenetics in a nutshell.

chances are i shouldnt be posting research like this, probably get burned at the stake for being a heretic..

next up, cary preamp thermal scans. something that is audio/electronics (not bio-electrical) related.

 

[Celadon]

I guess I shouldn't have brought up the Mushrooms on an audio forum, but it sounds like we eat off the same type plate...

Audio thermal scans -- I think it was you that pointed out your use of a thermal imager, and reminded me I have a cheapie, I am working on 2 Keithley DMM's, one is repaired and works awesome the other -- I will be doing some of that imaging thing myself today.

I usually stay out of the food diet conversations with people --most folks don't want to hear it.
Actully lost a good friend of many years through an argument about the subject; funny he is the one that had the quadruple bypass,....

 

[sae-7125]

I guess I shouldn't have brought up the Mushrooms on an audio forum

no harm, no foul. its all good but the others viewing this patchwork quilt picture book thread might think we are a little bit odd. to each their own, within reason.

Actully lost a good friend of many years through an argument about the subject; funny he is the one that had the quadruple bypass,....

an argument can be healthy if both sides learn and adapt to a higher level of improved health, in this case. its amazing how bypass surgery is the ever increasing norm. i many not be vegetarian nor vegan but i have a better understanding as to the thoughts and ideas behind the motivations for that particular lifestyle "choice". once again, to each their own since everybody is different in their own special way, even identical twins.

I usually stay out of the food diet conversations with people

dont hold back, you'll get gray/grey hair and we cant have that. stress kills... hair color and can lead to going bald. although i am being a snark since most of us are going bald regardless of stress.

I am working on 2 Keithley DMM's, one is repaired and works awesome the other -- I will be doing some of that imaging thing myself today.

sounds like someone is having fun and making progress.

 

[Celadon]

I am actually getting serious here today, reading data sheets on the TLC271 chip right now, and figuring out the circuit -- In my mind I have a suspect that seems likely , an LM337L, In it's tiny packaging, it lives much to close to a couple other things that are wayyy tooo hot.
This is a great ride and yes we are moving along rather well at a brisk learning pace today.
My Supervisor has been overseeing my every move, making sure I am correct in my work - but now it seems she has gone to sleep... hmm I think they call that a Cat-Nap!

Stress is indeed a killer and, That IS one area I need to change -- I am actually finding today's learning and work, relaxing - especially now that the boss isn't looking.

Uh Oh, Supervisors awake gotta go!

Thanks for your inspriation and continuing menagerie.

Celadon

 

[sae-7125]

it lives much to close to a couple other things that are wayyy tooo hot.

oddly enough i see that type of "design" in most everything i repair or modify.

 

[sae-7125]

looks like a cmos programmable low power op-amp.

https://www.diodes.com/assets/Datasheets/TLC271.pdf

vs the 3 terminal adjustable regulator:

https://wmsc.lcsc.com/wmsc/upload/file/pdf/v2/lcsc/1811141221_Texas-Instruments-LM337LMX_C7947.pdf

**the fact that the spec sheet is suggesting a "tantalum" raises a few red flags, when the engineer wrote the spec sheet. seems like mlcc or film would be a far better recommendation.

 

[sae-7125]

cary SLP-98 thermal camera shots.


things are starting to warm up, look fairly balanced.


hot spots in the power brick, after a few minutes.


during one of the warm-up cycles it appears that the right channel bottles are a bit slower and 10-20f cooler after an hour of on/idle activity.

not the end of the world since tube spec accuracy is not +/- 0.01% so a mild variance is acceptable.

 

[Celadon]

Nice shots with plenty of detail -- Nothing like bottles aglow in the evening hours

I think I've found it !
So first off the TLC271 is not the chip that is in this unit, it has a Ti marked as M8408 <--- date code LN 393N LM393N. I have yet to look into what that is, living in the TLC's place, BUT I found that the LM393N
The SM says this is being used as a "low noise Negative Supply" -- I am supposed to have -7 V @ the output (Pin 6) and I have 1.5 V. Looks sto me like someone moved south.

The TLCxxx I think there is an improved one .... Everything up to that point check within spec, and that is the last PS check. There is a big fat 2W 22ohm Carbon Comp that is way too hot -- it measures correct in circuit --

Looks like I need to figure this out, and get a Digikey order ready.

BTW -- Hakko is having some kind of anniverary sale Aug 8.
I like dealing with them direct they always include some kind of little freebie with the order. I DID save a lot on my Fume extractor with one of their sales...

Onward we move, success-- she's right around the corner...---------->

My best

*** I just found out that the LM393N looks like a way different component than what should be there ... I need more time to look, but ...

 

[sae-7125]

BTW -- Hakko is having some kind of anniverary sale Aug 8.

definitely good to know, i might have worn out the pumps on the hakko solder extractor on my bench.

There is a big fat 2W 22ohm Carbon Comp that is way too hot -- it measures correct in circuit --

carbon comp are always problematic just like germanium diodes/transistors, in regards to longevity.

 

[Celadon]

So I just opened up the good working unit and it has the same LM393N, so I have more work to do -- time for a break.

 

[sae-7125]

finished up with this yesterday, crown dc-300a series ii power amp.


chassis not very deep like most of the crown stuff i have worked on but it is quite heavy.


butt shot with speaker terminals hiding under the power caps and this amp can do stereo or bridged mono for extra punch.


side profile propped up with a stick, usual scrap piece of "almost" 2x4 found at any lumber yard or diy store.


the usual TS inputs which will need some rca adapters for performance testing. interesting to see the mains input frequency range of 50-400hz. apparently this could be used on a plane, aeronautical power system is usually 400hz.

The Ins & Outs Of An Aircraft's Electrical System

Even the most critical components of aircraft such as the flight control systems require electricity to function properly.

simpleflying.com

 

[sae-7125]

a few info links about the amp. heavy is the head that wears the crown, or one heck of a neck injury pending.

Heavy is The Head That Wears The Crown - Meaning and Usage

Literary analysis for the phrase Heavy is The Head That Wears The Crown from Henry IV with meaning, origin, usage explained as well as the source text.

literarydevices.net

https://ia804705.us.archive.org/4/items/JL11157/Crown%20DC-300A-II%20Power%20Amplifier%20Service%20Manual_text.pdf

thank goodness this amp is new enough to have a pair of pots for each channel...


... since adjusting the bias would require removal of the pcb, a time consuming process.


rare to see a specification for how many watts at idle a person should expect, definitely helps.

https://www.crownaudio.com/en/site_elements/dc-300aii-reference-manual

Crown DC300A Series II Anyone?

Was given 11 of these back in 93 or 4. Still have one that has scratchy pots & dusty. Opened the amp & cleaned house along with flushing ch1 & 2 pots. Plugged into some satellites and a sub - sounds excellent! Damping from 10-400Hz ------whoopie :-) Then my wife grabbed it. Soooo - the...

www.tapeheads.net

Crown DC-300A II Restore with Measurements

Hello Everyone! This is the first of several posts I’m going to make in this thread. This is the first time in a few years that I’ve posted on an online forum and will try not to make a mess of it. Background This is yet another DC-300A II refurbish experience that in my case was world’s...

www.diyaudio.com

a deeper dive in the next post.

History Files: The Crown DC300 Amplifier Leads The Solid-State Revolution - ProSoundWeb

A marvel of power density that revolutionized pro audio in 1967...

www.prosoundweb.com

speaking of revolution, around the same time:

When the Beatles Finally Got Political With 'Revolution'

The Beatles released their legendary protest song 'Revolution' as a B-side on Aug. 26, 1968.

ultimateclassicrock.com

 

[Celadon]

Interesting about the 400 Hz Aircraft usage you mentioned.
I wonder what a 155 rMS WPC amp would be used for on an aircraft, of course I am only thinking in terms of audio, wouldn't think the Flight attendant would need 155 W to tell passengers to fasten their seat belts, the Inflight movies would need some sort of amplification but.....

Me not familiar with aircraft systems.
Maybe I should take the train ....
I do have some Mundorf Caps that are intended for railroad something or other.

Another interesting journey to start the day.

 

[sae-7125]

I wonder what a 155 rMS WPC amp would be used for on an aircraft

if a luxury plane is involved who knows what might be installed.

i wonder if a large jet were to be gutted to accommodate passengers and a theater/sound room if the acoustics would be decent. active noise control designs have come a long ways since the 1950s.

Take a look at 10 of the world's largest passenger planes, from the Boeing 747-400 to the Airbus A380-800

The Airbus A380-800 is the world's largest passenger aircraft with a maximum capacity of 853. It seats 193 more passengers than the Boeing 747-400.

www.businessinsider.com

Evolution of Active Noise Cancellation (ANC)

ANC technology has been quite an important advancement. With constant human presence around us, it's now a necessity rather than a luxury.

www.copperpodip.com

 

[sae-7125]

crown interior photos.


disconnecting the pots is clearly optional. plenty of wire length to fold the face plate downward.


it is nice to see 4 pots in attendance even though they are hiding with this camera location.

 

[Celadon]

A luxury jet didn't even cross my mind- I was thinking strictly passenger, makes sense.
I don't know enough about acoustics to talk about turning a jumbo jet into a concert hall.

My work continues -- It is nice to have 2 identical units, so I fired up both and let the get to temp, startd with the thermal gun, and then with a thermocouple, measuring a lot of individual components, both units run about the same, and they have a tiny transformer that runs 83 F, by itself.
3 carbon comps that I will be replacing, have seen way to much heat for way to long.. maybe a couple other things.

The thing is, both unit's measurements are right on ...
There is an error in the service manual between the IC chips, but ...
I am buttoning these up, will do an order, and who knows whats -- plenty of other things to do...


Exit stage right ----->