Sony service manual - values do not correspond with actual components - Page 1
Forum section: electronics / projects

author: sanchaz12
author_rank: Regular Contributor
timestamp: September 04, 2019, 09:37:17 pm
content: Hi everyone,I have some questions regarding the service manual of a Sony product (European 'AEP' (220V-240V) DAV-S800 in this case).Some capacitors on the power supply board are bulging and have to be replaced. The weird thing is, the values of those caps on the board do not match the values in the service manual for the exact model I have. I can safely assume they were not replaced before as the solder on those caps looks factory fresh like the other joints.Another weird thing is that the values do match with another region in the service manual (US, CND, MX models) but that should not be for the region I have (AEP). Even the model identification on the back of the unit leads to it being for the 'AEP' region.Below are some snippets from the service manual, with the actual value of the capacitors installed noted below it.Installed capacitors are both rated 2200µF 35V. This should be correct for the US, CND, MX region, not AEP.The notation of 'S800' is unclear to me, does that mean "For all S800 models regardless of region" or "S800 models only from this region"?Installed capacitor is rated 2200µF 16V. This is again not the value as listed under the'Except US, CND, MX'column.The real question is, am I reading the service manual correctly or do these deviations happen more often? Perhaps a redesign of the power supply after publication of the service manual where they merged the different regions together and just used the highest value capacitors to be able to use it on any voltage?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 05, 2019, 01:35:57 am
content: Your deductions could be right, you do know many companies build or make some worldwide boards/designs etc ... they could have change ideas to be cost effective ?? or standardize parts values ...or you have boards who where supposed to be used in Usa Canada etc ... but maybe due to inventory reasons they where used in your country ?

author: amyk
author_rank: Super Contributor
timestamp: September 05, 2019, 01:46:02 am
content: If they're decoupling capacitors subjected to different voltages varying with mains input, then the largest value and highest voltage rating is always safe.Posting some pictures of the schematics with those components shown will help determine their purpose.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 05, 2019, 05:54:48 am
content: For C 921, 923, 2200uF is simply the next highest "preferred value" to 1800uF, so won't matter as their tolerance ranges actually overlap.For instance, if a design asked for an ideal value of 2000uF, a manufacturer would choose between those two values as the most economical practical substitute.The higher voltage rating is actually a good thing.For C933, 2200uF is quite a jump compared to 1000uF, but a good rule of thumb is, (within reason),"When you get to electrolytic caps of quite high capacitance values, those values are unlikely to be critical."The fact that the North American countries required the higher capacitance may point to a regulatory requirement for power supplies in those countries, rather than any direct technical reason.Or it could be something as simple as there being a large price difference between the lower & higher capacitance values in whatever country the PSU boards were produced.I remember seeing Sony equipment & individual PCBs made in Europe, as well as as Japan, & I know they were also made elsewhere.Your PSU PCB may have been made in the USA, Mexico, or perhaps, Malaysia, & would reflect the supply chain in those countries.Perhaps the price differential changed, so it was just as cheap to use 2200uF caps in all versions.If the device has worked for many years with the installed values, go with "what is on the board".It is worthwhile trying to "second think" some manufacturers, but very rarely with Sony!

author: sanchaz12
author_rank: Regular Contributor
timestamp: September 05, 2019, 07:25:20 pm
content: Quote from: amyk on September 05, 2019, 01:46:02 amFor what I can see C921 and C923 are in parallel on the +27V line for the amplifier board. C933 is on the +13V line for the 5.6V regulator 'IC905'.I just noticed that in the values (see first post) for C921 and C923 they call for a25V1800µF capacitor in the AEP model, wouldn't that exceed the rating of those capacitors as the voltage on that line is27V?I measured the voltage on the terminals of the'To AMP board'connector and it measures 28.1V (under load, while connected to the amplifier board), so a 25V capacitor would not be happy being on that line I assume.Below is the schematic for the power board with the capacitors mentioned outlined in red.

author: amyk
author_rank: Super Contributor
timestamp: September 06, 2019, 12:37:17 am
content: A 25V cap may survive slightly more... that and the lower capacitance suggests this might be an attempt at planned obolescence by extreme cost-cutting, only limited to those regions where they know their customers are more willing to be screwed over or have shorter warranties1800/25V is the cheapest option, followed by 2200/35, and then 2200/50. An examination of warranty policies in those regions may reveal a correlation. Since a 25V cap won't suddenly explode when given 25.1V or even 28V, someone may have initially calculated that they would be "good enough" to make the product last just beyond the warranty, but then due to other factors (maybe failing a bit too soon) they stopped doing it, which is why your specimen is different.This isn't the only case of something like this happening:https://www.eevblog.com/forum/repair/philips-uses-part-exceeding-max-rating/

author: vk6zgo
author_rank: Super Contributor
timestamp: September 06, 2019, 01:30:17 am
content: Quote from: amyk on September 06, 2019, 12:37:17 amStill, not what I would expect from Sony!It could just be a typo, too.Not in the same class, but many years ago, I bought a nice cheap, AM CB radio from K-Mart.For a "cheapie" it really looked good-----nice big "S meter", attractive chrome panel, & so on.It received well, too, the only drawback was that I couldn't seem to talk to anyone!I took it to work, had a look at the output with an Oscilloscope, & found it was only capable of about 1-2% modulation.Comparing the real thing with the schematic included in the operator's manual, (imagine, a schematic in aK-Mart product!), I found that a coupling capacitor actually fitted to the microphone amplifier was 0.0047 uF, but was shown as 0.47uF on the schematic, which was a much more logical value.Fitting the correct value cap restored the modulation to normal.Looking at the Parts List (OK, BOM if you insist), I found the incorrect value cap listed.Fairly obviously the assemblers diligently followed the Parts list---- I wonder how many disappointed CB-ers "gave up on the whole idea" from such a radio.Re the other thread:-Philipshavebeen guilty of some dumb things in the past-- much more so than Sony, but the 40" flatscreen referred to in that thread is probably a "badge engineered" Chinese cheapie!

author: sanchaz12
author_rank: Regular Contributor
timestamp: September 06, 2019, 06:54:05 pm
content: Thanks everyone for clearing up the information! I did not expect Sony to pull this kind of planned obsolescence on a product that was fairly high-end compared to other systems at the time...I replaced C921 and C923 with the same value that was originally there (2200µF 35V) as it is on a fairly high-power circuit. C933 was replaced with a 1000µF 16V cap as that is the only value I have at hand that would fit, and it is within 'spec' of the voltage on that line. The mains hum that was present before the replacement of the caps is now gone completely.