[TechAssist] Re: RCA TV F20601SE CTC175A won't regulate 140V B+
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 08 Jul 2005 09:35:40 -0400
Oh, very sorry- I meant to say jungle, not micro. I did change the
eeprom with one from another working set, so maybe parameter 18 is off.
I'll check into that. I'll also see about the manual regulation idea.
Might or might not have a chance today to work on it.
The schematic I'm using is a SAMS efact #3254 and it shows pin 29 and 30
of the jungle IC to have 3.7V each. I am wondering about Q4153 base and
collector which they label as 0.7V each.
Thanks for the help.
Gary
Gary McCartney
McCartney Electronics
Guelph Ontario Canada
Est. 1984
email: gary (at) number63.ca
Wayne Vanaman wrote:
> You said pin 30 of the micro, did you mean micro u3101 or jungle u1001?
> Pin 30 of the micro is a tone control best I can tell.
>
> My schematic shows u1001p29 as 6.1v, pin 30 at 3.52.
>
> There is an adjustment in the service menu, parameter 18, so I guess the
> jungle, micro, or eeprom could cause this. Or the parameter could be
> out of wack.
>
> I believe I would break to circuit from pin 30 of the jungle, you used
> R4162, and sub an adjustable power supply to see if you can manually
> "regulate" the circuit.
>
> Wayne Vanaman
> Omega Electronics
> 6904 W Fairfield Dr
> Pensacola, Fl. 32506-3310
>
> Wayne@xxxxxxxxxxxxxxxxxxxxx
> WWW.PensacolaTVRepair.Com
>
> 850-456-5995 voice
> 850-458-6369 fax
>
>
> Gary McCartney wrote:
>
>>Wayne, thanks for your help.
>>
>>I still can't pin-point the culprit, although I am now suspecting the
>>micro. Q4153 is being driven too hard. If I replace R4162 (100 ohm) with
>>a 47k, the set will regulate at 132V B+ because this forces Q4153 to be
>>driven less, allowing Q4151 base to conduct.
>>
>>I have replaced all the transistors involved- Q4150 with a TIP122 which
>>is what the number stamped on the original is, Q4151 with an NTE287 or
>>MPSA42, and I now have a 215495 from a scrap set- different area of
>>circuit- installed for Q4153. All act exactly as the originals did in
>>the circuit.
>>
>>The micro, pin 30 is exactly 3.7V as the schematic indicates, but pin 29
>>is high, ( 4.58V with B+ on variac at 130V, although goes down to 4.1V
>>as B+ raised to 139V.) which connects to Q4153 base, causing it to be
>>driven too hard. I've checked all the resistors in the circuit.
>>
>>Has the micro ever been known to cause this problem?
>>
>>Thanks,
>>
>>Gary
>>
>>
>>
>>
>>Gary McCartney
>>
>>McCartney Electronics
>>Guelph Ontario Canada
>>Est. 1984
>>email: gary (at) number63.ca
>>
>>
>>
>>
>>
>>
>>
>>
>>Wayne Vanaman wrote:
>>
>>
>>>Monitor the collector voltages of q4153 and q4154. The voltages should
>>>increase and decrease inversely as the B+ goes up or down. If not
>>>suspect a bad q4153/4. If it does look at q4150.
>>>
>>>R4169 passes the 12v run supply to the collector of q4153
>>>
>>>q4153 215495- smd, high failure
>>>q4151 146851
>>>q4150 217309
>>>
>>>The jungle outputs a regulator voltage. The path into the micro is the
>>>141v supply by way of R4157 and r4163, in series, with r4171 and r4158
>>>in parallel to ground at the r4163/r4157 junction. You also have 39k
>>>r4127 between U1001p29 and p30.
>>>
>>>Wayne Vanaman
>>>Omega Electronics
>>>6904 W Fairfield Dr
>>>Pensacola, Fl. 32506-3310
>>>
>>>Wayne@xxxxxxxxxxxxxxxxxxxxx
>>>WWW.PensacolaTVRepair.Com
>>>
>>>850-456-5995 voice
>>>850-458-6369 fax
>>>
>>>
>>>Gary McCartney wrote:
>>>
>>>
>>>
>>>>RCA TV F20601SE CTC175A won't regulate 140V B+
>>>>
>>>>This set came in dead, with F4150 open clean (not black looking) and 12V
>>>>regulator outputting 6.2V only. Replaced these and eeprom plus power
>>>>tact switch. Now set will fire up when run on variac at 95V AC.
>>>>
>>>>I can't figure out why the power supply won't regulate at 140V. It will
>>>>go higher than 140V if I crank up the variac toward 120V ac..
>>>>
>>>>Have done the following:
>>>>
>>>>-Replaced regulator output Q4150 with TIP122
>>>>
>>>>-replaced Q4151 with MPSA42 (NTE287 exact)
>>>>
>>>>-replaced C4150 10uF 200V & C4155 2.2uF 200V
>>>>
>>>>-replaced Q4153 surface mount #215495 with MPSA06 surface mount
>>>>
>>>>-Measured R4175, R4155, R4150, R4153, R4154, R4152, R4169, all OK.
>>>>
>>>>-Measured:
>>>>
>>>>-12V reg out-ok, 4.8V on eeprom pins 6, 8 -ok,
>>>>
>>>>-U1001 pin 30= 3.7V -ok
>>>>
>>>>-U1001 pin 29 should be 3.7V -measures 5.2V but as viac is raised, the
>>>>5.2V comes down close to 3.7V it should be
>>>>
>>>>-Q4153 B= 0.688 V, E=0V, C= 0.044V. C on SAMS schematic show it should
>>>>be 0.7 but I can't see why if the base is high, why C should read much
>>>>more than zero. My measurement agrees with me, not the schematic. Wonder
>>>>if mis-print or my mis understanding? Replaced this transistor with same
>>>>results.
>>>>
>>>>-Q4151 This transistor is not conducting because output of Q4153 is low.
>>>>B= .044V, E= 0V, C= 138V or whatever I have variac set at.
>>>>
>>>>- Q4150 reg out: depends where I have variac set but tracks the voltages
>>>>proportionally ok. No change since installing new part.
>>>>
>>>>-Q4151 This transistor is not conducting because output of Q4153 is low.
>>>>
>>>>Only other thing I can think of is to check the main B+ filter cap.
>>>>
>>>>Any other help appeciated.
>>>>
>>>>Gary
>>>>
>>>>
>>>>
>>>>
>>>>Gary McCartney
>>>>
>>>>McCartney Electronics
>>>>Guelph Ontario Canada
>>>>Est. 1984
>>>>email: gary (at) number63.ca
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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