LEECH666
Member
Last Activity: 02-06-2024, 06:08 AM
Joined: 01-15-2021
Location: S-H
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Ah that is good to know. I will at least lift one of the legs of the capacitors or even desolder them completely with my desoldering station. -
Can't see any leaking electrolyte on any of the caps and I won't have much time to work on the logic board this week. Maybe on Friday or Sunday. As mentioned these little transistor (or component) tester modules from AliE can measure ESR though probably not as accurate as a dedicated professional ESR meter.Leave a comment:
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I can measure the capacity and ESR with the transistor tester but I don't know how to measure leakage. Hmm ...
EDIT: Never mind, you meant checking for leaking electrolyte. Yeah sure. I can do thatLast edited by LEECH666; 01-22-2024, 07:56 AM.Leave a comment:
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You mean I should disable the voltage supply of the subwoofer amplifier IC U53? To check if the sub amp ic is causing the problems?...Leave a comment:
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Sure here are two clips of Music with / without sound bar. In the second clip I am disconnecting the power lines of the L/R channel amplifier boards to shut up the sound bar.
The sound at the subwoofer is obviously distorted and as mentioned previously all waveforms I have measured are total garbage quality on all devices (soundbar speakers, subwoofer module, headphone out). They sound vaguely fine (i.e. over the headphones) but a smooth crispy sine looks different the last time I checked. Now a difference between the bench setup I used to test the subwoofer module and...Last edited by LEECH666; 01-21-2024, 05:40 PM.Leave a comment:
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The audio signal looks in very bad shape on the scope on all outputs and I tested the subwoofer speaker module on the bench with a little Sure Electronics AA-AS32157 15W class D amplifier since it was the easiest to hook up to the module and the subwoofer speakers work fine when driven this way.
Ignore the German talking in the video it's not important (just me explaining to my non-technical friend for whom I am trying to repair the TV). I recorded this before I started this post and it just shows the setup and that the music sounds how it is supposed to sound when the subwoofer...Leave a comment:
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Hi Diah, sorry no I didn't notice your instructions. As mentioned I find your post hard to understand sometimes. It's probably a language barrier.
I did what you asked now and reverted everything and I can now confirm that the PSU coil buzzing is only happening when the +24V backlight connector (P201 as named in the BEKO PSU manual attached to one of my posts above) is connected. If the connector is disconnected the CFLs are off, no buzzing but also no change in audio behavior. It also looks like the audio PSU (YDK 192 in the schematics attached above) does not only power the sound...Leave a comment:
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So I made a video with some more information on how this is currently wired up and the various loading options I have available.
[B]Grundig 37 9880 T USB Some More Information and Loading Options[/B]
"Too long - no time to watch" Video Summary:
1) I think I connected the PSU PCB according to the previously provided description (provided by @Diah) but I could be wrong. The Logic Board is not connected to the PSU PCB but the Back Light inverter board is.
2) I have the following loading options: a programmable (Chinese) electric dummy...Last edited by LEECH666; 01-20-2024, 06:43 PM.Leave a comment:
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Oh "here goes nothing" is just a saying like "alright let's try this!" or "wish me luck". I wasn't refering to the function of the TV at all.
I measured the voltages with the +5VS connected to the 1K and BL, STBY and DIM pin connected the other leg. Everything connected but the logic board. All voltages (12V, 24V) are presents but no loud buzzing from the PSU. Just very very faint clicking every 1.5 seconds or so and I can observe my external, totally unrelated LED desktop lamp flicker at the same interval. Also the 12V seems more noisy to me now on the...Last edited by LEECH666; 01-20-2024, 06:43 PM.Leave a comment:
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I couldn't find any mention of it being LED based anywhere so I assumed it's still CFL based which may be incorrect. Anyway I connected the 1K between +5VS and STBY+BL pins. Here goes nothing.
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Thank you again for your help so far. Your short hand style of writing is a bit hard for me to decypher. I assume when you say "if the BL didnt power on" you mean "if the back light (24V to the inverter board on the left and the CFLs) do not power on", is that correct? The rest I think I understand. Anyway time to bust out the soldering iron....Leave a comment:
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+5VS seems to be too be the standby supply voltage as it is the only voltage being present after the TV is switched to standby via the remote.
So if I understood you correctly I should connect the +5VS pin via a 1K resistor to the STBY and BL pin like shown in the attachment?...Last edited by LEECH666; 01-20-2024, 08:48 AM.Leave a comment:
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Hi Diah, thanks for your reply. I have to admit that I don't know too much about TV PSUs. I read in the basic TV repair guide that the TV PSU waits for an "ok turn on"-Signal from the logic board. I assume this is the STBY labled pin on the connector that goes to the logic board but how do I get it to power up when the logic board is not connected? The STBY pin measures around 2.9V during operation when everything is connected ... so do I just apply 2.9V to that pin via an externally connected lab supply to turn it on?Leave a comment:
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Some scope screenshots attached ......
Last edited by LEECH666; 01-19-2024, 06:23 PM.Leave a comment:
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Grundig Vision 9 37 9880 T USB (Chassis SR) TV Repair Help - Distorted Subwoofer Sound and overall weird sound waveforms
Good day ladies and gentleman!
I am currently trying to repair a Grundig Vision 9 37 9880 T USB LCD TV for a friend that has a weird audio problem. Basically everything works fine except for the heavily distorted sound when the Subwoofer module is connected and there is a buzzing sound coming from the PSU PCB.
This seems to be a rather rare TV so there is not much prior on topic help to be found however a service manual is available at the usual sources (Electro Tanya i.e.).
I think the PSU buzzing comes from one of the coils near the bridge rectifier but...Last edited by LEECH666; 01-20-2024, 06:45 PM. -
I wish you all a wonderful day. Please let me introduce myself. I am LEECH666 from Germany.
Although I have been a member of this forum since January 2021, I have mainly lurked in the shadows and only participated in the forum by reading when I saw a benefit. For the most part, I've used badcaps.net as a resource for repair knowledge and well, bad capacitors, and to broaden my horizons in that regard. What prompted me to post my first introduction here is that I could use some help with a Grundig TV repair for a friend. I will also create a separate post for this. I have a degree...Leave a comment:
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