KB Transistor super 8 - UK Vintage Radio Repair and Restoration Discussion Forum

retroaudio · 18th Aug 2018, 11:35 am

I recently purchased one of these. The seller was running it from a 9 volt AC wall wart !!!!!!!!!. The original 4 pin battery plug had been cut off and I was left with three wires. I am going to run this off a PP9 battery however I was unsure if there is a right way and a wrong way to do it. The original battery would have been a pp11 which i believe is 2x 4.5 volt batteries in one box with two seperate positives and a single negative ?

regards Alex

crackle · 18th Aug 2018, 1:36 pm

Yes it is possible to run the KB VP21 Rhapsody Super 8 from a single 9v PP9.
The original PP11 battery was two separate 4.5volt batteries but they were connected in series at the 4 pin plug, the resulting centre tap went to the speaker. So in effect what you had was +4.5 0v -4.5v.
You can ignore the centre tap wire (it was orange in my radio) and just connect the battery +ve and -ve terminals direct to the on off switch.
You do not need the 0 volt connection, the two 200uf capacitors form the return path for the speaker that is needed for the amp to work.
I have previously been advised that you should ensure that the two 200uF electrolytic caps C23 & C24 are both in good condition.
See photo.

Click image for larger version

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If the detail is too small in the photo in this thread then use this link below to link to a larger photo on my website.
http://www.kbmuseum.org.uk/kb_images...b-vp21-pp9.JPG
Mike

crackle · 24th Aug 2018, 9:22 pm

I wonder if the OP actually came back to see the reply I left to help him.

Mike

jonnybear · 24th Aug 2018, 10:45 pm

Yes it is nice to get some sort of feedback when you have taken the time to reply to queries.

John

18th Aug 2018, 11:35 am	#1
retroaudio Pentode Join Date: Mar 2005 Location: Cairneyhill, Fife, UK. Posts: 135	KB Transistor super 8 I recently purchased one of these. The seller was running it from a 9 volt AC wall wart !!!!!!!!!. The original 4 pin battery plug had been cut off and I was left with three wires. I am going to run this off a PP9 battery however I was unsure if there is a right way and a wrong way to do it. The original battery would have been a pp11 which i believe is 2x 4.5 volt batteries in one box with two seperate positives and a single negative ? regards Alex

18th Aug 2018, 1:36 pm	#2
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: KB Transistor super 8 Yes it is possible to run the KB VP21 Rhapsody Super 8 from a single 9v PP9. The original PP11 battery was two separate 4.5volt batteries but they were connected in series at the 4 pin plug, the resulting centre tap went to the speaker. So in effect what you had was +4.5 0v -4.5v. You can ignore the centre tap wire (it was orange in my radio) and just connect the battery +ve and -ve terminals direct to the on off switch. You do not need the 0 volt connection, the two 200uf capacitors form the return path for the speaker that is needed for the amp to work. I have previously been advised that you should ensure that the two 200uF electrolytic caps C23 & C24 are both in good condition. See photo. If the detail is too small in the photo in this thread then use this link below to link to a larger photo on my website. http://www.kbmuseum.org.uk/kb_images...b-vp21-pp9.JPG Mike Last edited by crackle; 18th Aug 2018 at 1:47 pm.

24th Aug 2018, 9:22 pm	#3
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: KB Transistor super 8 I wonder if the OP actually came back to see the reply I left to help him. Mike

24th Aug 2018, 10:45 pm	#4
jonnybear Octode Join Date: Nov 2010 Location: Cullompton, Devon, UK. Posts: 1,435	Re: KB Transistor super 8 Yes it is nice to get some sort of feedback when you have taken the time to reply to queries. John