11th Apr 2019, 4:56 pm | #61 |
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Re: Ferguson 382U Firefly not playing ball
OK, can you double check C36 and C37 that do the same decoupling for V3 on pin 8.
Switch to MW with the volume turned up and turn on. using just one probe of your meter (we will use it as an aerial to pickup noise so you can stretch the other lead out but keep it away from yourself) touch the probe to the junction of R16 and R17. I would expect some hum. |
11th Apr 2019, 6:55 pm | #62 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Hi PJL - If I've got that junction right, it corresponds with a leg on one of the wafers and also to a piece of tag board on the end of some black wire. Placing the probe on the wafer lug gives nice click, but alas no hum.
Pete |
11th Apr 2019, 8:01 pm | #63 |
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Re: Ferguson 382U Firefly not playing ball
Try at the grid of V4 and see if you get hum.
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12th Apr 2019, 10:36 am | #64 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Hi PJL, just a distinct click..
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12th Apr 2019, 12:29 pm | #65 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Checking out resistors again - found R20 had come off one leg and, was 35k instead of 27k to boot. Replaced. R10 is open circuit! Replaced.
N.B. I've noticed a large watty resistor that goes across either C55, 56 or 57 and meets pin 9 of V5 is now getting hot after a couple of minutes! Pete |
12th Apr 2019, 12:54 pm | #66 |
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Re: Ferguson 382U Firefly not playing ball
Hi Pete.
I have a Ferguson "Firefly" 382U in my collection of radios. I admit it is not one of the easiest to get results from. The cog on the wave change shaft had totally shattered and I managed to ask someone to make me a replica in brass. It brings back memories of when my grandparents had a Ferguson 382U when they lived in rural Suffolk in the early 1960's, so I had to get one for myself. The F.M/VHF on mine is very weak, so unless the UCC85 grid resistors in the "dreaded can" have actually gone beyond accepted tolerance. There is life on the other bands, but not that much. The loud speaker on mine required replacement. Regards Mike |
12th Apr 2019, 1:04 pm | #67 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Hi Mike!
This one belongs to my parents and I remember it well as a small child - it was prob our main Radio before someone gave my Dad a broken Stereogram, which he fixed. I can see a couple for sale on eBay, however this one definitely has sentimental value to me, so if I could get it going, it'd make a great kitchen radio I reckon.. Pete |
12th Apr 2019, 1:16 pm | #68 |
Octode
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Re: Ferguson 382U Firefly not playing ball
Hi Pete
I hope that you can achieve your aim on this radio, as it does look really good! It is a shame that towards the end of the valve/tube era, manufacturers did not seem to care about the quality of some of the passive components used resistors used. Capacitors in those days did improve with size, but metal foil was not a great improvement over waxed paper. Resistors seemed to have been sampled from a really cheap source of supply. What amuses me about that era is that most people blame the actual valve on the failure of the radio, and of course that could not be further from the truth! Good luck Mike |
12th Apr 2019, 1:39 pm | #69 | |
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Re: Ferguson 382U Firefly not playing ball
Quote:
The "watty" resistors in this set are R30 500R 6W, R40 100R 6W and R41 250R 6W. They are meant to get hot. Your reference to C55 and C56 suggests that the resistor in question is R30. Did you mean C47 rather than C57? It's conceivable that the resistor referred to is R24 1.5k, but it's only rated at 1W.
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12th Apr 2019, 1:55 pm | #70 |
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Re: Ferguson 382U Firefly not playing ball
Circuit extract attached.
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12th Apr 2019, 2:07 pm | #71 |
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Re: Ferguson 382U Firefly not playing ball
Don't jump the gun, stay out of the FM box until MW is working!
I am a little concerned that you are replacing parts that were working earlier. R10 for example must have been working as you had a working oscillator. Are you trying to measure resistances when the resistor is still wired into the circuit? Lets go back to basics and measure the voltages again: V2 pins 2, 6, 7, 8, 9 V3 pins 2, 7, 8 V4 pins 6, 8, 9 All measurements to be taken with the waveband switch on MW. |
12th Apr 2019, 4:10 pm | #72 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Okay measurements on these pins are as follows:
V2 pins 2, 6, 7, 8, 9 ( 0.56, 197, 14.5, 107,14.3 ) V3 pins 2, 7, 8 ( 0.84, 198, 77 ) V4 pins 6, 8, 9 ( 0, 1.3, 143 ) Pete |
12th Apr 2019, 4:13 pm | #73 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
I feel something is not consistent here too, that hot resistor ( shown in the pic ) is not getting hot like it was this morning!
It's the colour coded one, not the "mains dropper" looking one. Pete |
12th Apr 2019, 4:32 pm | #74 |
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Re: Ferguson 382U Firefly not playing ball
V2 pin 1 - can you measure this one (pin 7 was my mistake).
V2 pin 9 - should be -ve? V3 pin 2 - is this -ve? V4 pin 8 - is this -ve? If it is can you check the value of R24 (6.8M ohms). High value resistors always fail by increasing in value and this one is already very high. |
12th Apr 2019, 4:46 pm | #75 |
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Re: Ferguson 382U Firefly not playing ball
The hot resistor is R29 (trader) and is 1.5K (body-end-spot) that matches the value in the manufacturers sheet. Power resistors will get hot under normal working conditions (otherwise they would use the smaller wattage type!).
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12th Apr 2019, 5:08 pm | #76 |
Tetrode
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Re: Ferguson 382U Firefly not playing ball
Hi - apologies, I should have recorded the polarity!
V2 pin 1 145.8V V2 pin 9 -11.8V V3 pin 2 -0.7V V4 pin 8 +1.0V Unfortunately, neither my Analogue or DVM have ranges that'll measure more 5M ohms, however I can see that there is 1.1V across it, if that helps at all? Thanks, Pete |
12th Apr 2019, 5:25 pm | #77 | |
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Re: Ferguson 382U Firefly not playing ball
Quote:
I'd say that the most likely reason for it getting TOO hot is C47 being electrically leaky. What voltage do you measure at the C47 end?
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12th Apr 2019, 5:26 pm | #78 |
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Re: Ferguson 382U Firefly not playing ball
V2 pin 9 is -ve so the oscillator is still running OK.
V2 Pin 1 is high but HT is high too so probably OK. V4 pin 8 is +ve which is odd particularly as you are adding 10M ohms to earth when you take the measurement. The anode is also a bit high which is the opposite of what is expected with a +ve grid voltage. Have you got a replacement UABC80? It would be worth cleaning the valve pins and socket and checking the cathode V4 pin 7 is securely tied to earth. |
12th Apr 2019, 5:28 pm | #79 | |
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Re: Ferguson 382U Firefly not playing ball
Quote:
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12th Apr 2019, 5:33 pm | #80 |
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Re: Ferguson 382U Firefly not playing ball
Sorry. I should have read posts #11, #12 and #27.
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