18-08-2019, 01:03 PM
Not sure what the maximum voltage rating of those fairly small resistors is. They can die fairly quickly if over-volted.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
Grundig 80U
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18-08-2019, 01:03 PM
Not sure what the maximum voltage rating of those fairly small resistors is. They can die fairly quickly if over-volted.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
18-08-2019, 02:14 PM
Some small resistors are about 200V rating. I use two in series if it has more than 150V. No way to tell other than maker's data sheet. One issue can be the spiral trim?
18-08-2019, 02:17 PM
0.6w maximum working voltage 250, if within power rating according to the specification sheet. I suppose they're so small that maximum means absolute.
At least the valve survived. Amie.
18-08-2019, 04:32 PM
(18-08-2019, 11:59 AM)Amie Wrote: Red black black orange space red? 200K 2% right? . I bet the original wasn't 2% Amie! Just looking at the values on that schematic, I'm surprised that they don't follow the usual logarithmic series, widely used here since before the war. Yet, with FM coverage, not to mention the valve line-up, that set is well post war. 'Preferred values' started off with 6 values per decade and a tolerance of ±20%. As manufacturing methods improved, ±10% tolerance was easily achievable and the number of values increased to 12. These series are known, respectively, as E6 and E12 - I'm guessing here but the E probably stands for exponential. Other ranges with even tighter tolerances and values per decade exist - thus your 200k ±2% samples - and ±5% seems to be the norm these days but, for all but rare instances, for the vintage kit we are discussing here, the E12 range is sufficient. I created a chart some years ago to illustrate the three main series and how neatly the tolerance of each value butted up neatly with the next value in the series. I thought I'd posted it here but can't find it so here it is and another for illustrating the maximum voltage for each power rating: Note the maximum voltages highlighted in yellow. Some manufacturers can provide resistors with higher voltage limits but they are very rare. If you look at the range of values - all, except the volume control, as far as I can see in round figures - you will see that there is no rhyme or reason for using them instead of standard values.
Hello Terry.
The Pye TV I mentioned earlier has some resistors with a pink band for tolerance and some have no band at all, what is the significance ? The 80U was made in 1955, I understand Germany had vhf FM long before the UK, Thanks, Amie. (18-08-2019, 04:49 PM)Amie Wrote: The Pye TV I mentioned earlier has some resistors with a pink band for tolerance and some have no band at all, what is the significance ? A pink band used to signify a high stability resistor, often with a gold band next to it (+-5% tolerance) or a red band (+-2% tolerance): https://www.flickr.com/photos/anachrocomputer/287693395 No tolerance band means the tolerance is +-20% Lawrence.
18-08-2019, 06:08 PM
(This post was last modified: 18-08-2019, 06:08 PM by Mike Watterson.)
USA FM late 1930s Band1, switched to 88 - 108MHz in 1945. Though they never did valve portable FM sets except one novelty super-rengen model as it was sold as HiFi.
Germany 1949 due to allies taking many German MW & LW allocations, so unlike UK where VHF-FM was really only for better Third Program/Radio 3 from 1955 to early 1970s, there were many German VHF-FM stations NOT on AM. So battery FM sets from 1953 (DC90) and then DF97 triodised mixer osc in same circuit from 1955. From 1955 to 1959 there were quite a few near HiFi battery Portable AM/FM German sets. Most had rechargeable LT (also acted as regulator). Some had a mains valve for Audio when not on battery. Some were push pull. Also UK roll-out was slow as the main aim was interference free Third Program in South East. Also simple UK duplication of the main 3 UK BBC and poor signal levels meant even in 1960s the VHF transistor portable was almost a waste of money in the UK. No VHF FM in Ireland till 1962 (except for UK reception in some places) and then only a copy of "Athlone". The UK had regional radio till 1939 and it wasn't revived by BBC till late 1960s or early 1970s, just before UK Commercial FM.
18-08-2019, 08:00 PM
(18-08-2019, 04:49 PM)Amie Wrote: I understand Germany had vhf FM long before the UK They did indeed, for the reason that Michael gave. Also, Grundig portable radios covered the full US FM band up to 108MHz long before the European band was extended: initially the top end was 100MHz, then 105MHz before the final 108MHz was reached. I always assumed that it was a clever way of earning dollars because they could sell them to US servicemen with a guarantee that they would still work in the US when they took them home. E12 resistor ranges were the norm long before 1955, though!
19-08-2019, 07:52 AM
Grundig had sales & distribution using the Majestic brand in the USA. Their valve based stereo decoder was initially only for the USA market.
The US export models would actually have been illegal in some European countries. Switzerland was the last to legalise import & ownership of FM radios extending above 104MHz
19-08-2019, 11:08 AM
(17-08-2019, 10:35 AM)Terry Wrote: Hi, Amie, I must admit that when I last worked somewhere where we used isolating transformers, the RCBO hadn't been invented (as far as I know!) I was wrong! I mentioned this to my electrician who directed me to this patent application dating back to 1965. No indication as to when they might have first appeared in the UK, though. |
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