Hacker Hunter FM volume R4 - UK Vintage Radio Repair and Restoration Discussion Forum

Findlay · 30th Jan 2019, 3:44 pm

I've got a strange thing happening with my Hacker Hunter on FM and I wonder if anyone can help? I can't seem to find the Hacker Group - does anyone know if it is still going?

The problem is that the set works fine for about 10 minutes tuned in to radio 4 and then the volume deteriorates until the signal is lost completely. If I re-tune I can pick up Radio 2 OK but no other stations. AM works fine. If I switch off and wait 10 minutes or so everything returns to normal! Any ideas?

paulsherwin · 30th Jan 2019, 4:00 pm

My first guess would be that this is the dreaded Lockfit problem, and one of the BF19x transistors is on the way out. You'll find lots of info about Lockfits if you search the forum.

Lots of forum members have more Hacker experience than me though, and may have other suggestions.

Nuvistor · 30th Jan 2019, 4:04 pm

Hi Findlay.

Which Hunter is the radio RP38 or RP38A? There are some changes, especially to the FM tuner.

There are quite a few possible reasons for the fault, how much fault finding experience have you and have you any test equipment?

Findlay · 30th Jan 2019, 4:16 pm

Thanks for the quick response guys! I'm pretty sure it is the RP38 as it just has the single tone control. Had a bit of fault finding experience but no test equipment apart from a DVM!

Sorry if this post is duplicated - I seemed to have problems posting. Thanks for the quick response guys! I'm pretty sure it is an RP38 as there is only single tone control. Have a bit of fault finding experience but no test equipment apart from a DVM....

Station X · 30th Jan 2019, 5:24 pm

As a new member your first few posts will require moderator approval. I'm doing my best while at the same time repairing a modulation meter!

Nuvistor · 30th Jan 2019, 5:27 pm

Manufacturers service sheet. Paul is probably correct about lockfits which may be a problem if it’s a fault in the VHF tuner, not the easiest to work on.
https://www.service-data.com/product...34/3502/m12634

Standard fault finding, take some voltage readings with the radio working and then faulty. The readings may be slightly different using a DVM than an Avo 8.

Lots of experience on the forum with Hacker, much more than I have.

Findlay · 30th Jan 2019, 5:38 pm

Thanks Graham and Paul. I'll get the manual and start measuring!

Thanks to Frank for the manual link!

Hunts smoothing bomb · 30th Jan 2019, 6:07 pm

Hello and welcome,

I'm going to suggest something now that I know I'm going to run the risk of having eyes "rolled" at me and I can see the shaking heads already but....

Are the batteries in tip-top condition?
This is exactly the sort of behaviour that exhausted batteries exhibit as whilst the set is switched off they recover a small amount of capacity and can work for a few minutes until the local oscillator stops, tuning down to the lower frequency end of the scale where radio 2 is may just be enough for it to start again, just an idea...

Cheers

Nuvistor · 30th Jan 2019, 6:09 pm

An excellent suggestion, I am guilty of taking these things for granted.

paulsherwin · 30th Jan 2019, 6:20 pm

Absolutely, never ignore the obvious things.

It's also worth cleaning the switchgear thoroughly if you haven't done so already. Dirty contacts can produce all sorts of strange symptoms.

Findlay · 30th Jan 2019, 9:29 pm

Thanks Lee and you other guys. Great ideas! I'd checked the batteries when first had problem and the thought the voltage was OK. I cleaned the switches and I checked the batteries again - I'm using two AA battery packs (12 batteries) and the combined voltage on switch on tonight was 16.92 V. After about 10 mins running on FM R4 this dropped to 16.55 V and I lost reception. Oddly reception came back a bit as I touched the battery terminals with the DVM probes. I replaced the AA packs with some PP9s with a voltage of 19.0 V and it has been running OK for about an hour. It almost seemed like the frequency for R4 had shifted a bit as well. This is strange as I can normally run the AA packs down to about 13V or so (1.1V per cell). When I put the AA cells in my other more battered Hunter (same model) they worked fine. Something still seems wrong somehow!

Hybrid tellies · 31st Jan 2019, 10:57 am

Taking this further you need to check the supply voltage to the FM tuner, this could be lower than it should be due to maybe a dried out electrolytic capacitor on the supply feed to the tuner. As you have got another Hunter which is working correctly you could do some comparison checks.

Findlay · 31st Jan 2019, 11:05 am

Thanks Simon - I'll check this out.

Findlay · 31st Jan 2019, 1:02 pm

I've just measure a few of the voltages on the tuner. Results are:

Faulty set:

Pin 1 : FM 4.18V AM 1.3V
Point A : FM 6.69V AM 1.9V

Good set:

Pin 1: FM 1.59V AM 0.78V
Point A: FM 12.06V AM 4.71V

The manual says they should be:

Pin 1: FM 0.55V AM 0V
Point A: FM 12.5V 4.4V

Does this help? The faulty set is certainly way down on the point A voltages!

Hunts smoothing bomb · 31st Jan 2019, 1:31 pm

Excellent, we are now getting somewhere!!

Indeed the set should still work at this reduced voltage but it has now pointed us in a direction to pursue.

What is point A? is it the supply rail to the tuner?
Also when the set dies on FM, does it also do the same on AM?

Cheers

Findlay · 31st Jan 2019, 1:53 pm

Thanks for getting back. Point A is described as the supply to VHF tuner (HT1). The set still works on AM when it dies on FM.

mhennessy · 31st Jan 2019, 2:18 pm

For me, Hunters with poor FM are the worst of all the faults to deal with. I can normally get them working to an acceptable state, but it's rare that I can make them work as well as the best examples.

Unlike most other Hacker sets, they are especially fussy about battery voltage when on FM. If you live in a good FM reception area, you might never notice this, especially if your example is one of the better ones. However, around here, it's a real problem.

I start by checking all the resistors that drop down the battery voltage to the IF and RF stages. Being carbon-comp, they always go high. Don't take too much notice of the voltages indicated in the manual, as I've no idea where these come from, and you can waste a lot of time trying to find out why yours are different.

Obviously the decoupling capacitors are worth checking for leakage. They are usually the Philips blue axial types, which have an extremely good reputation in my experience, so innocent until proven guilty. It really saddens me when people change them all on-spec, especially when they fit the radial type.

Having got the supplies to reasonable levels (ask me tonight and I'll check my notes), then I'll consider RF and IF alignment. This often helps a bit; sometimes a lot. Not recommended if you don't have the right gear, though many will argue that you can do without. Not really for FM IMHO.

After that, then it's looking for faults. Lockfits can fail, resistors go high, caps fail. FM faults can be caused by corroded leads on capacitors inside the AM IFTs - that takes some finding the first time you meet it! Basically, I've seen it all with these sets.

FM sensitivity faults are extremely rare on other Hacker sets. I guess the Hunter was just a bit marginal and relies on everything being 100%.

Findlay · 31st Jan 2019, 2:53 pm

Thanks so much for this Mark. You helped me a lot a few years back with a Hunter via the Hacker group site and as I couldn't seem to find the site any more I was a bit worried whether you were ok. I hope you are well.

mhennessy · 31st Jan 2019, 3:48 pm

Hi Findlay,

No problem

The Yahoo group is still there, but somewhat harder to navigate since Yahoo changed the interface a few years back. Perhaps one day we'll think of an alternative platform, but we're all pretty busy at the moment.

https://groups.yahoo.com/neo/groups/...adiogroup/info

Cheers,

Mark

Hunts smoothing bomb · 31st Jan 2019, 5:10 pm

Hi Findlay,

I was unsure as do not have the schematic for this set but I was guessing that point A was the supply to the FM tuner

I've just had a look at a schematic for an RP18 (sovereign) and I don't know if similar but when switched to FM the 18v supply from the two PP9's is dropped to the tuner by a low value resistor, (820 ohms in this case) this resistor is somewhere local to the AM/FM switching and separate from the tuner.

The fact that your voltage supply to the tuner (point A) is so low tells me that I should go hunting for the series resistor and check the value, I think I would also check any supply rail decoupling caps in the FM tuner too as if leaky they will pull the supply down after this resistor.

Hope that helps.

Cheers

30th Jan 2019, 3:44 pm	#1
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Hacker Hunter FM volume R4 I've got a strange thing happening with my Hacker Hunter on FM and I wonder if anyone can help? I can't seem to find the Hacker Group - does anyone know if it is still going? The problem is that the set works fine for about 10 minutes tuned in to radio 4 and then the volume deteriorates until the signal is lost completely. If I re-tune I can pick up Radio 2 OK but no other stations. AM works fine. If I switch off and wait 10 minutes or so everything returns to normal! Any ideas?

30th Jan 2019, 4:00 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,940	Re: Hacker Hunter FM volume R4 My first guess would be that this is the dreaded Lockfit problem, and one of the BF19x transistors is on the way out. You'll find lots of info about Lockfits if you search the forum. Lots of forum members have more Hacker experience than me though, and may have other suggestions.

30th Jan 2019, 4:04 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Hacker Hunter FM volume R4 Hi Findlay. Which Hunter is the radio RP38 or RP38A? There are some changes, especially to the FM tuner. There are quite a few possible reasons for the fault, how much fault finding experience have you and have you any test equipment? __________________ Frank

30th Jan 2019, 5:24 pm	#5
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Hacker Hunter FM volume R4 As a new member your first few posts will require moderator approval. I'm doing my best while at the same time repairing a modulation meter! __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

30th Jan 2019, 5:27 pm	#6
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Hacker Hunter FM volume R4 Manufacturers service sheet. Paul is probably correct about lockfits which may be a problem if it’s a fault in the VHF tuner, not the easiest to work on. https://www.service-data.com/product...34/3502/m12634 Standard fault finding, take some voltage readings with the radio working and then faulty. The readings may be slightly different using a DVM than an Avo 8. Lots of experience on the forum with Hacker, much more than I have. __________________ Frank

30th Jan 2019, 4:16 pm	#4
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Thanks for the quick response guys! I'm pretty sure it is the RP38 as it just has the single tone control. Had a bit of fault finding experience but no test equipment apart from a DVM! Sorry if this post is duplicated - I seemed to have problems posting. Thanks for the quick response guys! I'm pretty sure it is an RP38 as there is only single tone control. Have a bit of fault finding experience but no test equipment apart from a DVM....

30th Jan 2019, 5:38 pm	#7
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Thanks Graham and Paul. I'll get the manual and start measuring! Thanks to Frank for the manual link!

30th Jan 2019, 6:07 pm	#8
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: Hacker Hunter FM volume R4 Hello and welcome, I'm going to suggest something now that I know I'm going to run the risk of having eyes "rolled" at me and I can see the shaking heads already but.... Are the batteries in tip-top condition? This is exactly the sort of behaviour that exhausted batteries exhibit as whilst the set is switched off they recover a small amount of capacity and can work for a few minutes until the local oscillator stops, tuning down to the lower frequency end of the scale where radio 2 is may just be enough for it to start again, just an idea... Cheers __________________ Lee

30th Jan 2019, 6:09 pm	#9
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Hacker Hunter FM volume R4 An excellent suggestion, I am guilty of taking these things for granted. __________________ Frank

30th Jan 2019, 6:20 pm	#10
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,940	Re: Hacker Hunter FM volume R4 Absolutely, never ignore the obvious things. It's also worth cleaning the switchgear thoroughly if you haven't done so already. Dirty contacts can produce all sorts of strange symptoms.

30th Jan 2019, 9:29 pm	#11
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Re: Hacker Hunter FM volume R4 Thanks Lee and you other guys. Great ideas! I'd checked the batteries when first had problem and the thought the voltage was OK. I cleaned the switches and I checked the batteries again - I'm using two AA battery packs (12 batteries) and the combined voltage on switch on tonight was 16.92 V. After about 10 mins running on FM R4 this dropped to 16.55 V and I lost reception. Oddly reception came back a bit as I touched the battery terminals with the DVM probes. I replaced the AA packs with some PP9s with a voltage of 19.0 V and it has been running OK for about an hour. It almost seemed like the frequency for R4 had shifted a bit as well. This is strange as I can normally run the AA packs down to about 13V or so (1.1V per cell). When I put the AA cells in my other more battered Hunter (same model) they worked fine. Something still seems wrong somehow!

31st Jan 2019, 10:57 am	#12
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,965	Re: Hacker Hunter FM volume R4 Taking this further you need to check the supply voltage to the FM tuner, this could be lower than it should be due to maybe a dried out electrolytic capacitor on the supply feed to the tuner. As you have got another Hunter which is working correctly you could do some comparison checks. __________________ Simon BVWS member

31st Jan 2019, 11:05 am	#13
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Re: Hacker Hunter FM volume R4 Thanks Simon - I'll check this out.

31st Jan 2019, 1:02 pm	#14
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Re: Hacker Hunter FM volume R4 I've just measure a few of the voltages on the tuner. Results are: Faulty set: Pin 1 : FM 4.18V AM 1.3V Point A : FM 6.69V AM 1.9V Good set: Pin 1: FM 1.59V AM 0.78V Point A: FM 12.06V AM 4.71V The manual says they should be: Pin 1: FM 0.55V AM 0V Point A: FM 12.5V 4.4V Does this help? The faulty set is certainly way down on the point A voltages!

31st Jan 2019, 1:31 pm	#15
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: Hacker Hunter FM volume R4 Excellent, we are now getting somewhere!! Indeed the set should still work at this reduced voltage but it has now pointed us in a direction to pursue. What is point A? is it the supply rail to the tuner? Also when the set dies on FM, does it also do the same on AM? Cheers __________________ Lee

31st Jan 2019, 1:53 pm	#16
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Re: Hacker Hunter FM volume R4 Thanks for getting back. Point A is described as the supply to VHF tuner (HT1). The set still works on AM when it dies on FM.

31st Jan 2019, 2:18 pm	#17
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Hacker Hunter FM volume R4 For me, Hunters with poor FM are the worst of all the faults to deal with. I can normally get them working to an acceptable state, but it's rare that I can make them work as well as the best examples. Unlike most other Hacker sets, they are especially fussy about battery voltage when on FM. If you live in a good FM reception area, you might never notice this, especially if your example is one of the better ones. However, around here, it's a real problem. I start by checking all the resistors that drop down the battery voltage to the IF and RF stages. Being carbon-comp, they always go high. Don't take too much notice of the voltages indicated in the manual, as I've no idea where these come from, and you can waste a lot of time trying to find out why yours are different. Obviously the decoupling capacitors are worth checking for leakage. They are usually the Philips blue axial types, which have an extremely good reputation in my experience, so innocent until proven guilty. It really saddens me when people change them all on-spec, especially when they fit the radial type. Having got the supplies to reasonable levels (ask me tonight and I'll check my notes), then I'll consider RF and IF alignment. This often helps a bit; sometimes a lot. Not recommended if you don't have the right gear, though many will argue that you can do without. Not really for FM IMHO. After that, then it's looking for faults. Lockfits can fail, resistors go high, caps fail. FM faults can be caused by corroded leads on capacitors inside the AM IFTs - that takes some finding the first time you meet it! Basically, I've seen it all with these sets. FM sensitivity faults are extremely rare on other Hacker sets. I guess the Hunter was just a bit marginal and relies on everything being 100%.

31st Jan 2019, 2:53 pm	#18
Findlay Triode Join Date: Jan 2019 Location: Chelmsford, Essex, UK. Posts: 47	Re: Hacker Hunter FM volume R4 Thanks so much for this Mark. You helped me a lot a few years back with a Hunter via the Hacker group site and as I couldn't seem to find the site any more I was a bit worried whether you were ok. I hope you are well.

31st Jan 2019, 3:48 pm	#19
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Hacker Hunter FM volume R4 Hi Findlay, No problem The Yahoo group is still there, but somewhat harder to navigate since Yahoo changed the interface a few years back. Perhaps one day we'll think of an alternative platform, but we're all pretty busy at the moment. https://groups.yahoo.com/neo/groups/...adiogroup/info Cheers, Mark

31st Jan 2019, 5:10 pm	#20
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: Hacker Hunter FM volume R4 Hi Findlay, I was unsure as do not have the schematic for this set but I was guessing that point A was the supply to the FM tuner I've just had a look at a schematic for an RP18 (sovereign) and I don't know if similar but when switched to FM the 18v supply from the two PP9's is dropped to the tuner by a low value resistor, (820 ohms in this case) this resistor is somewhere local to the AM/FM switching and separate from the tuner. The fact that your voltage supply to the tuner (point A) is so low tells me that I should go hunting for the series resistor and check the value, I think I would also check any supply rail decoupling caps in the FM tuner too as if leaky they will pull the supply down after this resistor. Hope that helps. Cheers __________________ Lee