Sony STR-DE635 recieiver won't power up

[ampapa]

First off I'd like to say, "Hello." to the group. I hope I can gain
some knowledge from the group's collective input.

I have a Sony STR-DE635 stereo receiver that will not turn on and I
would like to investigate into maybe seeing if I can repair it. I
found a set of schematics on this site which I believe will
definitely help.(http://www.eserviceinfo.com/index.php?what=search2)

I'm guessing but I think that the problem is related to the power
supply? On p.13 of this .PDF manual it has an A/C and D/C schematic,
this receiver has a seperate board for each. I probed the A/C board
and found that it has voltage out to the "Digital" board of a little
over 12 volts but when I try to test the pins on CNV902 I thought I
should be getting appx. 110 A/C but only get appx. 2? CNV902 is a
simple 2 wire connector leading directly to a transformer.

My common sense is telling me that why would I need a transformaer
the size of Kansas for only 2 volts A/C? So, I'm guessing this might
have something to do with it? I could be in left field due to my lack
of knowledge and inexperience, that's why I'm hoping you guy's/girl's
can shed some light.

Thanks for any suggestions or hints you can provide.

 

[Jerry G.]

These sets can be very difficult to reliably and safely troubleshoot and
service. The proper training, service experience, product training, and a
solid background in electronics theory would be an asset to do service on
these sets.

In going by the way you are presenting your questions, I would suggest you
give the unit out to an authorized service centre to have an estimate done
for you.

When servicing these sets, the main procedure is to verify all the voltages
from the power supply. If there are some missing, then you must start to
troubleshoot the unit from the point of loss, and go on from there. It is
possible that there is a short somewhere, and has damaged the power supply,
or some other components failed, and thus caused other types of damage.

It is very common in these receivers that the output devices and their
respective driver devices, become shorted. In this event, the power supply,
and a number of other support components may be damaged. You will have to
determine this.

--

Jerry G.
==========================


First off I'd like to say, "Hello." to the group. I hope I can gain
some knowledge from the group's collective input.

I have a Sony STR-DE635 stereo receiver that will not turn on and I
would like to investigate into maybe seeing if I can repair it. I
found a set of schematics on this site which I believe will
definitely help.(http://www.eserviceinfo.com/index.php?what=search2)

I'm guessing but I think that the problem is related to the power
supply? On p.13 of this .PDF manual it has an A/C and D/C schematic,
this receiver has a seperate board for each. I probed the A/C board
and found that it has voltage out to the "Digital" board of a little
over 12 volts but when I try to test the pins on CNV902 I thought I
should be getting appx. 110 A/C but only get appx. 2? CNV902 is a
simple 2 wire connector leading directly to a transformer.

My common sense is telling me that why would I need a transformaer
the size of Kansas for only 2 volts A/C? So, I'm guessing this might
have something to do with it? I could be in left field due to my lack
of knowledge and inexperience, that's why I'm hoping you guy's/girl's
can shed some light.

Thanks for any suggestions or hints you can provide.

 

[Mark D. Zacharias]

These models often have fuses sort of hidden under a circuit board attached
to the transformer. If these fuses are blown you probably have a blown amp
channel. Sometimes just the output transistors for a given channel are bad,
sometimes there are other small parts bad. Occasionally a circuit mod is
required to lessen the bias at startup.

Mark Z.

 

[ampapa]

Jerry,

Thanks for the response.

I realize that I am not qualified or have any experience in
electronics repair which is why I would deem this as a
hobby/experiement and not a profession.

Would it be outside the scope of this forum to ask if my logic in the
orignal post was corect? Does in fact the transformer expect to see
110v coming in from the A/C board?

"I probed the A/C board and found that it has voltage out to the

"Digital" >board of a little over 12 volts but when I try to test the
pins on CNV902 I >thought I should be getting appx. 110 A/C but only
get appx. 2? CNV902 is a

simple 2 wire connector leading directly to a transformer."

This in fact is what I am trying to establish.

When servicing these sets, the main procedure is to verify all the voltages
from the power supply.

Thanks for any additional help you can give.

AJM,

 

[ampapa]

Are you saying there would be a fuse physical under the board or just
hidden by another board? This thing has 6 fuses and all checked out
fine.

If the A/C board isn't putting out the correct voltage to the
transformer then certainly it's going to have problems. That's why I
was hoping someone would be able to tell by the schematics if in fact
the A/C board should be putting out 110, if not then what voltage
should I be looking for on CNV902?

Thanks.

 

[ampapa]

Sorry if this is a double post.

Mark, are you saying there might be a fuse literaly underneath a
circuit board and not necessarily hidden from view by a circuit board?
I checked about 5 or 6 fuses in this thing and all checked fine.

My biggest problem is that when I read the schematic I can't tell if
the transformer is supposed to be getting 110v from the A/C board on
CNV902? If it is then I can trace it from there. That's my real
dilema.

The schematic can be found here
(http://www.eserviceinfo.com/index.php?what=search2).

Thanks,

 

[Mark D. Zacharias]

If all the fuses are OK, then the power transformer probably isn't getting
voltage from the turn-on relay. Does it click when you press the Power
button? CNV902 gets no AC voltage to speak of til this relay fires. (I
assume your voltmeter is set to measure AC voltage)

Mark Z.

 

[ampapa]

No click when I push the power button and I do have my voltmeter set
to A/C.

By looking at the schematic am I correct that the transformer should
be seeing appx. 110v? or should I be looking for some other voltage
being delivered to the transformer?

Also, in order for the A/C board to "enable" the turn-on relay by the
on/off switch then I should be seeing voltage coming back from the
"Digital" board correct? I see the header that leads to the "Digital"
board has 4 legs, GND, 12V, P_OFF and P.RY. Are these designations
specific to the industry as to what they represent?


Thanks for the help,

 

[Mark D. Zacharias]

Measure from point 12V with respect to ground. I suspect your standby
transformer is bad.

Mark Z.

 

[ampapa]

The "standby transformer" is that T902 on the schematic?

I've got 13.5V on the header that leads to the "Digital" board.

 

[Mark D. Zacharias]

Well, you need to check the standby voltages on the digital board. Q1205
appears to be a 5 volt source.

Mark Z.

 

[ampapa]

I've got 3 readings at the transistor Q1205, the center leg 13.53 and
the 2 other legs 6.79 and 6.21 respectively. I think this is wrong,
the schematic shows the "base" at 6.5v?

 

[ampapa]

I've got 3 readings at the transistor Q1205, the center leg 13.53 and
the 2 other legs 6.79 and 6.21 respectively. I think this is wrong,
the schematic shows the "base" at 6.5v?

 

[Mark D. Zacharias]

I'd say that's close enough. You're going to have to see that the "5V" line
makes it to the microprocessor, and at this point you're going to have to
evaluate the reset line to the micro. Should toggle from ground to 5V when
you plug in the cord.

Mark Z.

 

[Mark D. Zacharias]

P.S.

If there's any history on this that I should know, now is definitely the
time to say. For example if there was a lightning strike involved.


Mark Z.

 

[ampapa]

Mark, thanks for your help.

"microprocessor" are you referring to the 8 pin IC1206?

I'm a bit confused at Q1205 the base reading is 13.53v, why? Shouldn't
that be more like 6.5v?

One thing that keeps bugging me is the P_RY leg from the A/C board. Is
this the return leg to the transformer on the A/C board? It's
currently reading 0v.

Also, before I flipped the "Digital" board over I noticed some red
crayon looking markings around the 2 IC's 1205 and 1207. When I
flipped the board over it looks as though they've been soldered on? I
don't think this has been worked on, so I thought I would make mention
seeing as we were in the area and it looked strange.

 

[Mark D. Zacharias]

comments inserted.

Mark, thanks for your help.

"microprocessor" are you referring to the 8 pin IC1206?

It does appear that the reset pulse comes from IC 1206 pin 8. The
microprocessor is IC 1201.

I'm a bit confused at Q1205 the base reading is 13.53v, why? Shouldn't
that be more like 6.5v?

This is a somewhat unusual circuit,but that voltage certainly looks wrong.
The transistor Q1205 might be shorted, and / or IC 1206 might be bad.
Unfortunately, if this places 12 to 13 volts at the cathode of D1211 (1208)
the microprocessor may very well be fried.

One thing that keeps bugging me is the P_RY leg from the A/C board. Is
this the return leg to the transformer on the A/C board? It's
currently reading 0v.

This line would probably toggle to 5v or so to turn on the relay if the
receiver were working properly. It's not, so you see nothing here.

Also, before I flipped the "Digital" board over I noticed some red
crayon looking markings around the 2 IC's 1205 and 1207. When I
flipped the board over it looks as though they've been soldered on? I
don't think this has been worked on, so I thought I would make mention
seeing as we were in the area and it looked strange.

Maybe some prior factory rework. I don't think I'd worry about it at this
point, unless the work looks really sloppy or something's obviously wrong,
like a wire hanging and shorting against something, etc.
<snip>


This repair is going nowhere fast. It would be nice to have another digital
board to sub.

Oh, well.


Mark Z.

 

[ampapa]

Mark,

I spoke with my friend this afternonn and this was a refurb from the
factory his sister used to work for a Sony call center, but until
recently the receiver was working fine. He was having a on/off issue,
no lightning strike.

I mistyped earlier the 2 IC's that looked like they were replaced are
IC1205 and IC1501 as well as D1207 and D1206. I tested the diodes with
my DMM it has a diode test and they appear to be O.K. (tested one
direction then flipped leads). I'm not sure how to test the IC's?

I took some readings on the 2 IC's (IC1025 and IC1501) and was getting
..25v on leg 1 on both and 0v on the other legs. I also checked IC1206
and here is how it layed out, definitely out of wack...

8 - 1.6v
7 - 1.25v
6 - 6.76v
5 - 0
4 - .35
3 - 1.83
2 - 2.37
1 - 13.53

I wasn't sure what to test on IC1201 did you want me to look at the
reset pin 90 for 5v?

My biggest understanding issue is how do I determine the flow on the
schematic?

"This repair is going nowhere fast. It would be nice to have another
digital
board to sub."

My posts take forever to show up on the forum is there a way to speed
it up??? As far as another board I don't think I can find one? do you
know anyone selling them, cost, etc.


AJM,

 

[Mark D. Zacharias]

I'm going to digest this for a bit and will post back later.

Meanwhile, if you're posting through Google, they only add posts once or
twice a day.


Mark Z.

 

[ampapa]

How can I post quicker so we can respond faster?