Philips 1201 (K30 series II) colour TV arc at switch-on - UK Vintage Radio Repair and Restoration Discussion Forum

ronbryan · 24th Feb 2019, 9:54 pm

When my K30 is powered up there is an arc from the bottom centre of the screen, below the black border and the sound also dips, indicating a momentary power supply trip. It does not always do this.

The spring connecting the tube dag coating to the beam current sense pcb is correctly positioned and tensioned.

I have discussed this with forum member 'Sideband' (an ex-Philips engineer) and he recalls that the problem was caused on some of these sets in production, by the decorative plastic trim around the tube rim charging up as the EHT rushes up. The static charge is collected by the metal insert in the trim and flashes over to the rim-band from the exposed ends, where the trim is cut at the bottom centre. This current surge then causes the momentary trip of the power supply, possibly sensed by the beam current limiting circuitry.

Sideband has said that factory 'fix' for the problem was written up in one of the Philips Service Link documents, probably around 1982/83. Does anyone still have a copy of this document or recall how it was recommended to be fixed?

Ron

Vectamart · 3rd Mar 2019, 8:17 pm

I have a number of 'Link' magazines from that era. I'll see if I can find the article.

ronbryan · 3rd Mar 2019, 10:34 pm

Vectamart

Thanks for offering to search your 'Link' archive.

Ron

24th Feb 2019, 9:54 pm	#1
ronbryan Octode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 1,959	Philips 1201 (K30 series II) colour TV arc at switch-on When my K30 is powered up there is an arc from the bottom centre of the screen, below the black border and the sound also dips, indicating a momentary power supply trip. It does not always do this. The spring connecting the tube dag coating to the beam current sense pcb is correctly positioned and tensioned. I have discussed this with forum member 'Sideband' (an ex-Philips engineer) and he recalls that the problem was caused on some of these sets in production, by the decorative plastic trim around the tube rim charging up as the EHT rushes up. The static charge is collected by the metal insert in the trim and flashes over to the rim-band from the exposed ends, where the trim is cut at the bottom centre. This current surge then causes the momentary trip of the power supply, possibly sensed by the beam current limiting circuitry. Sideband has said that factory 'fix' for the problem was written up in one of the Philips Service Link documents, probably around 1982/83. Does anyone still have a copy of this document or recall how it was recommended to be fixed? Ron

3rd Mar 2019, 8:17 pm	#2
Vectamart Pentode Join Date: Feb 2007 Location: Ventnor, Isle of Wight, UK. Posts: 141	Re: Philips 1201 (K30 series II) colour TV arc at switch-on I have a number of 'Link' magazines from that era. I'll see if I can find the article.

3rd Mar 2019, 10:34 pm	#3
ronbryan Octode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 1,959	Re: Philips 1201 (K30 series II) colour TV arc at switch-on Vectamart Thanks for offering to search your 'Link' archive. Ron