Radio set BCA495A (Algemeen)
door Pandu Rajan 
, 12.06.2023, 14:08 (529 dagen geleden)
Dear Friends
The above set is identical to the set BX495A. I presume few models of Philips Holland came to India in a kit form and were assembled here. This is one of the those sets. I am in the process of restoration of this set. While checking the wiring I have noticed one big mistake in the connection of the valve base for Valve B2 - EAF42. As per the component layout drg. pin no 3 diode D is connected to the junction of R21 and R23 and pin no 4 is connected to Cathode which is grounded. But in the set which I am restoring the connections are reversed. In this set pin no 3 is connected to ground and pin no 4 is connected to the junction of R21 and R23.
Now pin no 4 is the suppressor grid. I am unable to understand how the delayed AVC will work?
All the connections are original. I am unable to understand how this mistake went un noticed during manufacturing and testing and overall how the set was working all these years?
I am attaching the photo of the bottom of the set showing this mistake.
Regards
P.Rajan
![[image]](images/uploaded/2023061212083364870ac17a132.jpg)
Radio set BCA495A
door Ouwe Schipper , Sassenheim, 12.06.2023, 16:39 (528 dagen geleden) @ Pandu Rajan
Well, mr. Rajan
The suppressor grid being used as a diode plate is somewhat weird,
but I can't see why it would not work as such.
Not knowing the complete circuit diagram, I have no idea about the
influence this has in the performance of the pentode
Yours,
Nico
--
een kinderhand
is ook weer gauw leeg
Radio set BCA495A
door Pandu Rajan , 12.06.2023, 18:01 (528 dagen geleden) @ Ouwe Schipper
Dear mr Nico
Thanks your reply. You can refer the schematic for the set BX495A/ Bx490A.
Regards
P.rajan
Radio set BCA495A
door Ouwe Schipper , Sassenheim, 12.06.2023, 19:07 (528 dagen geleden) @ Pandu Rajan
I say, mr. Rajan...
The least you could do is inserting these diagrams in a posting
Just as Mr. Maurice suggested. I'm at your service, but I'm not
your servant
Nico
--
een kinderhand
is ook weer gauw leeg
Radio set BCA495A
door Pandu Rajan , 13.06.2023, 13:40 (528 dagen geleden) @ Ouwe Schipper
Dear Mr. Schipper
I am extremely sorry. Now I am attaching the following
1. Schematic for BX495A
2. Underside component drg. for BX495A showing the original wiring of B2.
3. Underside component drg for BCA495A ( BX495A) where the pin connection of 3 & 4 has been interchanged. I have marked with Red. this is also clear from the photo which I have sent earlier. The actual drg. of BCA495A is not available but both the sets are identical.
Kindly advice
Regards
P.Rajan
![[image]](images/uploaded/202306131135426488548ebd75d.jpg)
![[image]](images/uploaded/20230613113613648854ade63ce.jpg)
![[image]](images/uploaded/20230613114007648855972af36.jpg)
Radio set BCA495A
door Ouwe Schipper , Sassenheim, 13.06.2023, 22:15 (527 dagen geleden) @ Pandu Rajan
Well, mr. Rajan
The only answer I can think of, is:
Rather weird, but no harm done; but using the diode as a diode and
using the suppressor grid just as such, seems more logical to me.
Anyhow, my advice is restoring the situation equal to the diagram
Good Luck
Nico
--
een kinderhand
is ook weer gauw leeg
Radio set BCA495A
door Maurice 
, Dordrecht, 12.06.2023, 18:45 (528 dagen geleden) @ Pandu Rajan
First redraw both schematic parts of both the situations.
show them here.
Then chassis is nog GND-zero, its negative.
Look at R5-6 and C9
Also in your picture draw and make a note of every wire it is according to the situation.
Then see if your set is working in this setting.
--
"I haven't even turned this on to see if it works because as long as I don't it might"