Re: Toshiba TV model 27A44, Regulated B+ Info

Hi,

Note: Now I have the SM.

I fixed a lot of TVs over the years that had excessive HV, but this Toshiba is out of the ordinary. All the parts that would normally cause excessive HV in the horizontal sweep circuits tested fine. I removed parts from the circuit to test. The flyback pulse width on the scope was normal, within 11 to 14 usec at 10% from base. Note: Other FBT voltages were higher than normal. The SM, "Basic Adjustments", states the regulated B+ should be "+123 +/- .5V". This voltage, "+123V" or the HV, can not be found in any schematic in this SM.

The filter capacitor in the regulated B+ was tested. Due to the time already spent trying to repair this "DOG", I decided upon a couple modifications to save this TV from going to the dump. I installed a 5 ohm,

5 watt resistor in the B+ line to the FBT. I also added a .0012uf 2KV sweep cap across C412 .0027 1.25KV. Now the HV is around 27KV, which I checked several times during a long run, and the TV has a good picture.

Brad

Hi, > > I have a Toshiba TV (27" pic) model 27A44 (mfg. 05/04) in my TV service >shop (no SM). Customer told me the TV "sparks" once in awhile, then turns >off. It didn't do it in the shop yet, but checking the HV, it was 30KV >(higher than normal). I checked the regulated B+ and it measured +122V! >Unfortunately, there is no marking on PCB that indicates what this voltage >should be. > > I removed and tested the timing capacitors in the horizontal output >circuit. Sometimes an open capacitor will cause the HV to go higher >than normal. They tested just fine. > > 130V is very common in my experience, but can someone tell me what the >regulated B+ should be in this model TV? > > Thanks in advance, Brad > > Before you type your password, credit card number, etc., > be sure there is no active keystroke logger (spyware) in your PC.