TV Forums

Free Games TV Forums

  Main Index FORUM
HOME 		Search Posts SEARCH
POSTS 		Who's Online WHO'S
ONLINE 		Log in LOG
IN 		Rules & FAQ RULES
F.A.Q.

Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
Toshiba 1400 TB Blue Screen

 
 


Philip
New User

Feb 7, 2003, 8:26 AM

Post #1 of 8 (2480 views)
Shortcut
Toshiba 1400 TB Blue Screen Can't Post
The problem is that this set does not pick up any stations. The search function appears to be working as well as the channel selection (numbers are displayed on the screen). I have measured the tuning voltage (VT) as it searches for a channel and this appears to be OK but there is only 1Volt on the "BM" connector from the actual tuner unit on the main board which I believe could be the problem.
Can anyone help?

Regards
Philip



Alan
TV Repair Authority

Feb 7, 2003, 10:09 AM

Post #2 of 8 (2476 views)
Shortcut
Re: [Philip] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
What are the part numbers of the chips on the tuner?
Alan


BL_Thompson
TV Repair Authority

Feb 7, 2003, 9:29 PM

Post #3 of 8 (2473 views)
Shortcut
Re: [Philip] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Philip, is this an older TV? Most modern tuners are digital, although they may still have tuning voltage and band switching pins. Look for pins labeled data, clock, CE, etc. If these pins exist on your tuner, all you have to do is confirm B+ and eliminate any rf input problems to determine that you have a bad tuner (which is what I suspect). On rare occasions, there are other problems related to IF or tuner control. If you want to be as sure as possible, and you have access to an oscilloscope, check for activity on the data & clock lines... you may have to change channels to initiate a data transfer. If you confirm a bad tuner, I recommend PTS as opposed to new replacement.

BLT
-----------------------
Bryan Thompson
Spyder Byte Services
Albuquerque, NM


Philip
New User

Feb 14, 2003, 8:16 AM

Post #4 of 8 (2462 views)
Shortcut
Re: [BL_Thompson] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Thanks Bryan for your reply. The connections on the tuner are as follows. VT, AGC, BM and IF. There is a label on the tuner which has UF784 X 1 on it. What voltage should I expect to see on the BM connection?
Many thanks for your help.
Philip


Philip
New User

Feb 14, 2003, 8:25 AM

Post #5 of 8 (2460 views)
Shortcut
Re: [Alan] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Dear Alan,
There are no chips inside the tuner. only SMT mounted transistors on one side of the pcb and coils on the other.
Regards
philip


BL_Thompson
TV Repair Authority

Feb 14, 2003, 4:29 PM

Post #6 of 8 (2458 views)
Shortcut
Re: [Philip] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Philip, are you sure there are no other pins? BM is a band switching pin, but if that's the only BS pin, then I'm sure you have a digital tuner. If not, the BM voltage (sans schematic) is normally 12V.
-----------------------
Bryan Thompson
Spyder Byte Services
Albuquerque, NM


Philip
New User

Feb 17, 2003, 9:19 AM

Post #7 of 8 (2453 views)
Shortcut
Re: [BL_Thompson] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Hi Bryan,
I've checked the tuner voltage at the point BM and as you said there is 12volts present there. I have also tried doing a station search using both the "ASM" and ">>>" functions and it seems to be locking onto a channel but the screen remains blue and there is also no sound! so I wonder if it is the IF stage.

Regards

Philip


BL_Thompson
TV Repair Authority

Feb 17, 2003, 9:13 PM

Post #8 of 8 (2448 views)
Shortcut
Re: [Philip] Toshiba 1400 TB Blue Screen [In reply to] Can't Post
Check the menu for a way to turn off the blue screen... it may be labeled video mute or something similar. You need to be able to see the picture to properly diagnose the problem. If that doesn't help, I would suspect the tuner before the IF stage, but it's a gamble. You might try tapping around on the board and the tuner, if it's a bad connection somewhere, this might help you narrow it down.
-----------------------
Bryan Thompson
Spyder Byte Services
Albuquerque, NM

 
 
 


Search for (options) - Page loaded in: 0.19 s on (CGI/1.1)