• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Standby Circuit - Your opinion is needed

Status
Not open for further replies.

lynx

Member
Hi

i need some guidelines for the repairing of an old home theater...
probably some of you will say "why i bother and i don't get a new one"...

i'm not fan of such devices but if i manage to repair it i will make a
friend happy :)

the model is Philips HTS3164, the VFD is not working neither the power led..
there's no video output, thus looks like a dead unit.

the power supply voltages seem fine .. 12V, 32V (for the amplifier), 5V, also manually
ejecting the DVD tray it automatically closes when you connect the device to the
mains...also some of the ICs on the main board they do power on becauce
they get a little bit warm.

i'm thinking the problem might be the standby circuit...in the following
picture / schematic seems the standby is controlled by an MCU... P89LPC931
(it's the fine pitch IC in the second picture over the connector)

i need your help to diagnose if the problem is the standby circuit because
i'm not that expert with such kind of repairings...but i'm able with a little
bit help.

thank you
 

Attachments

Last edited:

lynx

Member
Hi

yes there is and it's 4.59V.

also i've noticed that if i remove the red 7 pin connector seen in the photo
on the previous post and then i connect the device to the mains, the
power button led finally turns on but of course nothing else works.

is this an indication that indeed the problem is in the main board?
 
Last edited:
There are two red connectors in the picture.

4.59 seems a little low. Is that when it's connected to the rest of the system or disconnected?

I think you have the service manual. Have you followed the TSS tree?
 

lynx

Member
There are two red connectors in the picture.

4.59 seems a little low. Is that when it's connected to the rest of the system or disconnected?

I think you have the service manual. Have you followed the TSS tree?

hi

i'm referring to the 7pin red connector, if you remove it the power button led turns on
4.59V everything connected, is low for the BK5V? what voltage i should expect?

also the manual indicates i should check the standby circuit.
 

crutschow

Well-Known Member
Most Helpful Member
I had a dead VCR with low voltage on the 5V standby supply and, as I was poking around, nearly burned my finger on a hot electrolytic capacitor.
It had gone bad and was leaking enough current to pull down the 5V.
Replacing it restored the VCRs normal operation.
You might check/replace all electrolytics to ground on the 5V.
 

lynx

Member
I had a dead VCR with low voltage on the 5V standby supply and, as I was poking around, nearly burned my finger on a hot electrolytic capacitor.
It had gone bad and was leaking enough current to pull down the 5V.
Replacing it restored the VCRs normal operation.
You might check/replace all electrolytics to ground on the 5V.
hi, thank you for your reply, most capacitors already replaced but i will check again...

i need a clarification, BK5V shouldn't be 4.59V? i think it's quite close to 5V with tolerance.
 

lynx

Member
Finally repaired, for anyone else searching tips for similar units i suggest refitting the cables to exclude bad conduction issues.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top