03-12-2013, 05:53 PM
I think a DAF91 will do a 1U5 with a base wire swop.
Lawrence.
Lawrence.
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hallicrafters tw-500
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03-12-2013, 06:14 PM
Lots of tech clues and info in the following ebay listing, although the price seems a little steep?
http://www.ebay.co.uk/itm/Zenith-Trans-O...tronics_R2&hash=item4d0addcd20 Colin
hi joe and guys, the schematic that colin kindly sent me , gives.... il6. iu4, iu4, iu5. 3v4, my set is fitted with dk96 ,df 86, df86,daf91, and a brimar [unknown] four of the d type are mullard ,the numbering is anything but clear , so the plot thickens, any suggestions chaps ?maitiu.
03-12-2013, 08:44 PM
(03-12-2013, 07:59 PM)standunmj Wrote: hi joe and guys, the schematic that colin kindly sent me , gives.... il6. iu4, iu4, iu5. 3v4, my set is fitted with dk96 ,df 86, df86,daf91, and a brimar [unknown] four of the d type are mullard ,the numbering is anything but clear , so the plot thickens, any suggestions chaps ?maitiu. The 96 series are 25ma heater current, the 91 is 50ma heater current, if they are all still connected in series then the heater shunt values need to be adjusted to compensate, don't forget that the shunts will also shunt the anode/screen currents. Personally I would investigate all the heater shunt resistors to see if they are the original specified values or if they have been changed at some time for different values, then take it from there. Let the forum know if they are the original values as specified in the schematic. Lawrence
03-12-2013, 09:04 PM
(03-12-2013, 08:44 PM)pwdrive Wrote:(03-12-2013, 07:59 PM)standunmj Wrote: hi joe and guys, the schematic that colin kindly sent me , gives.... il6. iu4, iu4, iu5. 3v4, my set is fitted with dk96 ,df 86, df86,daf91, and a brimar [unknown] four of the d type are mullard ,the numbering is anything but clear , so the plot thickens, any suggestions chaps ?maitiu. Forgot to add that if by any chance the output valve has 50ma heaters then that along with the DAF91 which is also 50ma will put a serious strain on the other 96 series valves which are 25ma heaters if the latter heaters haven't been sufficiently shunted, I would also check the heater feed dropper resistor as well which is switched in on mains operation. It would be handy to draw a schematic diagram of the whole heater chain as it stands so you can see what's exactly what. Lawrence.
04-12-2013, 09:28 AM
Could the whole '96' series valves (DK96, DF96, DAF96, 7 DL96, IIRC), not be used in these radios. As these all have 25mA heaters, there would be no strain put on any of them. I've just looked in my 1970 & 1971/72 editions of the Mullard Data Books, but they don't show any equivalents for the 1U5 or 1U4, and don't mention the 1L6 at all. For the
3V4 they give the equivalent as a DL94, but I don't have the detailed data to hand. My feeling is that the '96 ' range could be substituted for the earlier '91' series, which IIRC, are pin-compatible, but I'm not sure about the '94' valves, or the U.S. 1.... series.
04-12-2013, 10:00 AM
If running 25ma heater valves the series heater dropper resistor that's used on mains operation would have to be altered if operating the receiver on mains, there's all the shunt resistors too. I am not sure exactly how the shunt values are worked out, anyone know?
Lawrence.
04-12-2013, 10:05 AM
(03-12-2013, 06:14 PM)camallison Wrote: Lots of tech clues and info in the following ebay listing, although the price seems a little steep? On the ebay link, it would be set 2 that matched your requirements, if sourced from the US. Colin
04-12-2013, 10:15 AM
A brief explanation of why shunt resistors in directly heated valves connected in series are needed.
http://www.mullardmagic.co.uk/mullard/bl...s-iii.aspx Lawrence.
An even more detailed overview of shunt resistors pertaining to previous posts can be found in this Mullard publication.
It's in different sections of the document so scroll down all of it to find the relevant sections Lawrence. |
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