Deciding what caps to use

[dlucy]

I print out sheets to guide my restore:

Component Number, Old Values, New PN, New values

I highlight in yellow when I've pulled each old component out, then highlight in blue when I've replaced it with a new one. Makes the end result green-ish.
Wherever I've made a mistake or found an inconsistency, I circle or note in red.

Way too OCD, but it's the only way I can keep track of what I'm doing.

 

[dlucy]

Is there a preferred way to format the BOM?

Some people will want just text, two columns (PN then a space then qty) so they can drop it in the BOM tool

Others would LOVE to have a XLS or Google Sheets doc with all the other info so they can use that as the basis for their own work.

If you can provide both, you're an outstanding example of paying it forward.

 

[markthefixer]

Look at the lists in these threads, they have been successfully used.
When in a spreadsheet, the replacement parts numbers are kept in the same column, so it's east to just grab the parts numbers as text and drop them into the mouser import 500 lines tool.

 

[cuda440]

I have compiled a new spreadsheet with (I think) is all the latest info. My columns include symbol, value, voltage, tolerance, small description (film, electrolytic, BJT NPN, etc.), board, Mouser Part #, Original Part as Spec'd in service manual, and notes. I left off manufacturer and price.

I thought "what was originally spec'd" might be helpful so you could check what was coming off the board as you substituted the new parts.

While adding the Original Part column I ran across three discrepancies that I ask to be checked on:

On the tuner board this cap is different than the SM-
C66 10uF 50V 20% ELECTROLYTIC AWE-043 647-UPW1H100MDD .1uF, 25V

The last part listed on this same board is a transistor-
Q9 BJT PNP AWE-043 512-KSA992FBU 2SA725
but there are a Q10 and Q11 in the SM, both 2SA725, so I'm wondering if they should be added to the list and replaced with 992s.

On the protection board (AWM-025) is a 2SC945 transistor replaced thusly-
Q6 BJT PNP AWM-025 512-KSC2383YTA 2SC945
but the other 2SC945s on this board are replaced with 512-KSC1845FTA.

Please advise.

 

[dlucy]

On the protection board (AWM-025) is a 2SC945 transistor replaced thusly-
Q6 BJT PNP AWM-025 512-KSC2383YTA 2SC945
but the other 2SC945s on this board are replaced with 512-KSC1845FTA.

Please advise.

The KSC1845F is a very low noise small signal amplifier. That's great. You'd use it in places where the audio signal is critical (E.g. preamp). However, it can only handle a very, very small current. It's Ic max is 50 mA. So, you can't run anything but a small current through it, but it'll do amp duty with very little noise... so long as the current is low.

The KSC2383 is different. It is not low noise. But it is bigger, so it can dissipate more heat. And it can handle up to 1A of current. So, on a power-related board where the KSC2383 is doing voltage regulation or switching duty, instead of amplification, then the KSC2383 is better (than a low current device like the KSC1845F).

 

[dlucy]

On the tuner board this cap is different than the SM-
C66 10uF 50V 20% ELECTROLYTIC AWE-043 647-UPW1H100MDD .1uF, 25V

Please advise.

If I'm reading your post correctly, it looks like the original schematic part was a 0.1 uF 25V electrolytic cap... and the suggested replacement BOM part was a 10 uF 50V?

If I'mm reading that right, then two possibilities come to mind:

Someone made a simple decimal place mistake when looking up the replacement part for the BOM
or
This is a board-to-board coupling cap and that is often a place where the manufacturer skimped out and used a low-cost, low-capacitance cap and the BOM maker has specified a newer, much-better-at-coupling cap for that spot.
or
something someone smarter than me understands.

 

[dlucy]

[QUOTE="cuda440, post: 11347959, member: 264209"The last part listed on this same board is a transistor-
Q9 BJT PNP AWE-043 512-KSA992FBU 2SA725
but there are a Q10 and Q11 in the SM, both 2SA725, so I'm wondering if they should be added to the list and replaced with 992s.

Please advise.[/QUOTE]

Well... two things:

Yes, if you were replaced the 2SA725's, you'd replace them both. The KSA992 in that spot sounds right. But...

If you replace any of the transistors on the tuner board, you'll very likely have to align the tuner board. That is tricky, even for pros, and requires some significant equipment. Low end, old style, used from eBay cost at least $150 and on up from there. Like a Sencore SG-165, plus an oscilloscope, plus a sweep generator, plus some very, very good instructions. Can be done, but it's tricky and expensive.

Most folks here on AK replace the electrolytic caps on a tuner board and leave it at that. If you find a failed component, like a transistor or diode, then it's time to replace it... and know you probably have to re-align the tuner board. But if you don't think there is a problem, I'd recommend getting a few more opinions before replacing the semiconductors on a tuner board.

There is a thread that kinda wanders about a lot, but which contains some basic answers on aligning a tuner: http://www.audiokarma.org/forums/in...sible-for-an-amateur-to-align-a-tuner.668444/

 

[cuda440]

Okay, lets enumerate the three as A (cap off by 10x), B (Q10, Q11 love), and C (2383 vs. 1845, fight!).

A - looked like a typo to me too, but the replacement list in post 5 has been around for a while and would have thought it would have been caught a while ago. I'll wait a bit before inserting the .1uF in case someone knows a good reason to not.

B - Yes, I'm not certain I'll do anything to my tuner board given the possible complications, but still wanted to offer the complete list of parts for those who do, and it was part of the original post. I'll add Q10 and Q11 to the list.

C - The 2383 gets the nod.

I need to walk through the spreadsheet once more to make sure it's clean before I share it.

 

[markthefixer]

SX-737?

c - 2383 is discharging a 100uf cap through a 22 ohm resistor. Safe operating area is marginal for the 2sc945 and other replacements, but 2383 has larger die, lower VceSat so less heat is spread through bigger die, and thus longer life in a CRITICAL position.
b- a725 to a992 will NOT impact the tuner alignment if you are mechanically careful in their replacement.
a-C66 couples AM audio out of the tuner. 0.1uf on scat, in BOM, in 2013 I posted "AWE043 c66 0.1 25 cssa 598-DSF050J" dsf's are no longer available. 10uf is 100x larger, won't hurt anything - but I'd go with a WIMA cap nowadays. 505-MKS2D031001A00KI 0.1uf 100v 10%
which is a tape mounted cap - for longer leads than the bulk packaged caps at 2 - 3 mm.
I am not willing to dig further tonight / this morning to trace past 2013 and my posts as to if I were guilty of the typo or someone else.
but NO - I wouldn't and probably didn't come up with a change there.
NOW if SOMEONE found a FACTORY 10uf cap there, or a factory bulletin, I would consider differently.

 

[cuda440]

Thank you sir. I was hoping you would chime in on this and provide your expert (and historical) insight.

I'll update the BOM accordingly and post it here, hopefully today. I'm going to name it "proposed" so as to give AK a chance to review it for errors/omissions and to make any suggestions as to what might be added.

 

[dlucy]

Thank you sir. I was hoping you would chime in on this and provide your expert (and historical) insight.

I'll update the BOM accordingly and post it here, hopefully today. I'm going to name it "proposed" so as to give AK a chance to review it for errors/omissions and to make any suggestions as to what might be added.

If you would, please include Mark's comment on the PNP transistor replacements on the tuner board. It is advice easily missed deep in a thread and easier to find if near or with the BOM.

 

[cuda440]

One more thing - the trimmer resistors on the power amp board in the original BOM are of two types, vertical and flat, when entered in the Importer. From the BOM:
AWH033 vr1 100 652-3386F-1-101LF
AWH033 vr2 100 652-3386F-1-101LF
AWH033 vr3 10k 652-3296Y-1-103LF
AWH033 vr4 10k 652-3296Y-1-103LF

I was expecting all of them to be of the vertical multi-turn type. Here's the Mouser info:

Mouser #:
652-3296Y-1-103LF
Mfr. #:
3296Y-1-103LF
Mfr.:
Bourns
Customer #:
Trimmer Resistors - Through Hole 3/8" 10Kohms Sealed Vertical Adjust

and

Mouser #:
652-3386F-1-101LF
Mfr. #:
3386F-1-101LF
Mfr.:
Bourns
Customer #:
Trimmer Resistors - Through Hole 3/8IN 100 OHMS 10% 0.5Watts Square

Please confirm what is correct.

 

[markthefixer]

AWH033 vr1 100 652-3386F-1-101LF
AWH033 vr2 100 652-3386F-1-101LF
AWH033 vr3 10k 652-3296Y-1-103LF
AWH033 vr4 10k 652-3296Y-1-103LF

yes, as intended, the flat one VR1,2 100 ohms is for idle current and is a pita to crank and crank with a multiple turn pot for the adjustment

the tall one is VR3,4 10,000 ohms with 12 (or 25?) turns and is NEEDED to control the DC offset voltage (0.000v) at the output - THAT adjustment is TOO touchy with a single turn pot.

 

[cuda440]

Okay then, I think I have a completed BOM and will post it sometime today.

Thanks to markthefixer and dlucy for the expert help.

 

[cuda440]

How do I post the excel file? Upload a File gives me an error about the file extension.

 

[cuda440]

I get it, let the newbie figure it out for himself. The lesson is better learned that way.

Well I did. Convert it to a zip file.

And here it is:

 

[markthefixer]

Not - let the newbie figure it out, that can only be accused if the thread contributors can be proved to have posted in other threads during the interval in question.

I wasn't on from 10:30 am to 8:00 pm on thursday to see it...

 

[markthefixer]

p.s SX-737 bom, qx-949 bom, possibly a SX-434 bom, and then all the other threads, it's gonna be a while.

meanwhile I ripped up and replaced 16 sq ft of kitchen floor,
did a clutch,
cut up plywood to make a platform and installed stops to capture and hold the feet of the item on the platform, a
and made the equivalent of a wheeled furniture moving dolly in reinforced plywood (no center hole!!).
All while babysitting a flood prone basement during a rain and flood event.(more nervous energy than physical expenditure there)

to do:
washing machine repair - belt and pump
laundry
gut laptop computer to get at REALLY BURIED failed hard drive. replace with new 1TB drive, rebuild win 7 os and everything else on laptop.
try to recover as much as possible from failed drive - IF it failed and not that the OS was zorched somehow.

all before monday?

Oh, and somehow get my van past 100' of swamp between it and pavement (pesky rain and flooding!!! stranded van at back door!!))
for monday's mandated doctor's appointment and mandatory grocery shopping - no less MAIL the clutch I did.

oh - and ANOTHER clutch came in later today, with three more on the way!!

no moss growing here, now that the knee is returning to function.

 

[cuda440]

My bad. I believe offense was taken where none was intended. Having me figure it out on my own was a good thing.

I'm just hoping I can earn my keep here with contributions like a BOM that others can use, because I'm about to lean on AK heavily as I dive into in-and-out of protection problem of the SX-737 in question. Assuming that goes well I'll be following that up with the repair and restore of an SX-1050 that I picked up yesterday.

 

[cuda440]

I'm going to start a new thread to post the BOM shortly.