Sony ICF-SW30 Radio Repair

[dark_hawk]

Hi,

I'm trying to repair an old Sony ICF-SW30 Radio. The radio was in very bad condition when I got it. Ripped ribbon cables, detached screen solder joints and lots of dust.
I've been able to add jumper wires for the screen and the inter boards connections.

My problem now is that the volume coming out of the speaker is very low. While the sound coming from the headphone jack is ok.

Here is schematic and board layout:

1- The Speaker output part:

2- Schematic:

3- Board layout:


Link to service manual:
https://mega.nz/#!2hl01IQa!M28H2ZAEGXYkFjEhitOPf0wN9faJeiHKAuzDF56e90I

I checked several caps and the seemed ok (C61,C62, C109). I also checked a different speaker.

I think the power amp IC is ok since the headphones is working fine.

How do I located the competent causing the low audio level on the external speaker?

Thanks

[Haenk]

Did you bridge the upper contact in J1? Might be a lot of corrosion in there (acting as a resistor) - or try with some contact cleaning...

[dark_hawk]

Thanks for the reply.

J1 is the headphones jack, and it seems to be working fine.

I tried bridging the positive of the speaker with the positive of the headphones and sound level increased slightly. (Blue)

I also bridged the positive of the speakers with the input of resistor R48 (47 ohm and reads correctly) and sound increased considerably, but I still don't think that's the full output of the this speakers. (Red)

[dark_hawk]

The problem seems to be with output 1 (Pin 10) of IC3 which is the power amp. If I shorted pin 10 with pin 7 which is output 2 the speaker works normally.


Output 1 is connected to C55 and C52 and both are ok.

Where on out1 path is the problem?

I completed disassembled J1 which is the headphone jack and used a fine sand paper and cleaned it, but it didn't solve the problem.

[goaty]

Did you measure connection and wires to the speaker, maby it is not low resistance ?
You say headphone is good. Is it good on left and right channel ? Or only mono ? Asking because maby _input_ of amp is wrong.

[andy3055]

The speaker is driven by OUT 1. Check the C 61 470 uF/4 volt cap. Also make sure the speaker itself is good (out of circuit) and the cone moves freely.

[dark_hawk]

Did you measure connection and wires to the speaker, maby it is not low resistance ?
You say headphone is good. Is it good on left and right channel ? Or only mono ? Asking because maby _input_ of amp is wrong.

The speaker is fine. When shorting the input or the output 1 and 2 in IC3 Power amp is works fine.
I think it might be a problem with input as you say, but I can't figure out where.

The speaker is driven by OUT 1. Check the C 61 470 uF/4 volt cap. Also make sure the speaker itself is good (out of circuit) and the cone moves freely.

Speaker is fine. Also C61 is fine.

[dark_hawk]

I've been able to trace the problem to S2. There where some dead traces.

Thanks for all the help

[jebem]

Old thread but still a recurrent issue with tone switches on several Sony world receiver radios.

Common issue is related to heavy oxidation inside the tone witch contacts. Contact cleaner would not fix the issue in most cases. I had to remove the switch from the PCB and then dismantle the switch to be able to use fine sand paper to carefully remove the dark oxide layer.
 

[Kerlin]

Sony have too many of these problems in their expensive SW series radios.
NOT good enough they are very expensive here in Australia. Around 2002 I managed to beat the price of a SW7600G down from $A650 ($US600) to $A500.
It had the many problems that had already been identified and had not been fixed, including the electrolytic that was put in around the wrong way, which causes problems with SSB reception.
That problem with the SW30 ribbon is well known. I nearly bought one in H.K. glad I didn't.
As I said in a recent post these problems are due to the lack of a "field Trial" were the appliance is put out on a test to few consumers before the product is released.
I have never released on of my professional products without doing that first, its surprising what can be found and prevented.
Gave up on trying to get a good portable Rx with no stock problems and just use my Ham gear for SW reception now.
Have a few remote speakers around the house instead.