[TechAssist] Re: RCA TV F20601SE CTC175A won't regulate 140V B+
- From: Eric Manuel <tvman@xxxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 08 Jul 2005 19:16:57 -0230
Hi Gary I have the ctc175a zip file do you need it ..Eric
Eric
E M Electronics
Deer Lake Nfld
Canada
tvman@xxxxxxxxxxxxxxx
Gary McCartney wrote:
> Thanks for the message Dan, but I believe the CTC177 is diffrent than
> this. My chassis has a Darlington power transistor as the regulator output.
>
> My standby is 153V but I have the AC connected through a variac so the
> source is low, maybe 105 V ac or so.
>
> I have double checked everything now, parts values, continuity of
> traces, etc. and it is still not working. Q4153 is being driven too hard
> from the jungle IC, that is all I can think of. Still, when the scene
> changes on the screen, the jungle IC pin 29 outputs varying voltages to
> correspond to the scene brightness, so it appears the jungle is doing
> it's job. The 12V run supply to R4169 is bang on 12V. The base is at
> 0.688V but the collector is at 0.044V where it should be higher, like
> around 0.7V according to the print. When I manually feed in a voltage
> going to the base, I need to get around 1.6V on the collector before the
> set will run at 140V B+. with the ac input at 120V. Of course I have
> replaced the transistor but with exact same results.
>
> Something isn't adding up but can not figure it out. Even replaced
> filter caps C4153 and C4705 and added another cap across the main filter
> C4007.
>
> I'm thinking right now of either getting a new junlge LA7610 or giving
> up on it. Don't know what else to try.
>
> Oh by the way, I reinstalled the original eeprom and it seems to be
> working. Parameter # 18 will lower the B+ by 2V only.
>
>
>
>
> Gary McCartney
>
> McCartney Electronics
> Guelph Ontario Canada
> Est. 1984
> email: gary (at) number63.ca
>
>
>
>
>
>
>
>
> Webster's TV wrote:
>
>>Gary,
>>
>>Is your standby B+ voltage OK? Should be around 149V, if this is high, I
>>found a tip I had written down for this problem on a CTC177, that says to
>>change C4123 and R4125. Don't know if this will be of any help to you or
>>not, but thought I'd mention it anyway.
>>
>> Dan Webster
>> Webster's TV
>> Shullsburg, Wi.
>>----- Original Message -----
>>From: "Gary McCartney" <gary@xxxxxxxxxxx>
>>To: <techassist@xxxxxxxxxxxxx>
>>Sent: Thursday, July 07, 2005 5:34 PM
>>Subject: [TechAssist] Re: RCA TV F20601SE CTC175A won't regulate 140V B+
>>
>>
>>
>>
>>>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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