|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
12th Dec 2018, 4:33 pm | #1 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Kleinempfänger with lots of hum
Hello! I hace just replaced the electrolytic caps of 4uF and the radio has a very noisy hum even without antenna
I have also replaced the 0.9uF with a 1uF polyester cap Resistors seem to be fine. Which value are them? 2w? What do you think https://youtu.be/bAxtGcxwRtI
__________________
EA3IAV |
12th Dec 2018, 4:47 pm | #2 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
|
Re: Kleinempfänger with lots of hum
Did you fit the new caps the right way round?
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
12th Dec 2018, 5:17 pm | #3 |
Nonode
Join Date: Jul 2005
Location: Hull, East Yorkshire, UK.
Posts: 2,087
|
Re: Kleinempfänger with lots of hum
Dried out filter capacitors? That's what it seems like to me. They are only 4uf, but it looks like the speaker is the field coil type that also serves as a choke smoother.
Not a bad little radio as far as looks go and as simple as it gets electronically. No RF stage LW/MW with reaction & only one audio stage. The VCL11 is a double triode & the audio side must have quite a lot of gain. Was it specifically made for this radio and no other? |
12th Dec 2018, 6:25 pm | #4 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Re: Kleinempfänger with lots of hum
I am going to try this 4uF because I think that this hum comes from the AC
__________________
EA3IAV |
12th Dec 2018, 9:08 pm | #5 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Re: Kleinempfänger with lots of hum
I have tried this 4uF ones and it is the same noise
Also ferrites on the feed line
__________________
EA3IAV |
12th Dec 2018, 9:15 pm | #6 |
Dekatron
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,518
|
Re: Kleinempfänger with lots of hum
Are you sure the capacitors have been fitted correctly - I had the same problem with my Kleinempanger, and had managed to swap two connections on the smoothing circuit - result was a lot of hum!
__________________
Engineers make things work and have spare bits when finished |
12th Dec 2018, 9:53 pm | #7 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
|
Re: Kleinempfänger with lots of hum
Seconded. It's not immediately obvious which way round the smoothing capacitors should be connected in these sets. If in doubt the OP should connect a meter set to DC Volts across each smoother in turn and check that it reads the right way round.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
12th Dec 2018, 10:46 pm | #8 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Re: Kleinempfänger with lots of hum
Hello!
How come I have the same issue if I used a non polarized capacitor like the one i showed? Of isit possible that it has a little polarity?
__________________
EA3IAV |
12th Dec 2018, 10:55 pm | #9 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Kleinempfänger with lots of hum
Also the connection points of the "-ve" sides of the HT reservoir and filter capacitors matters as well, eg: they must not be connected together to a common point.
Lawrence |
13th Dec 2018, 1:00 am | #10 |
Octode
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
|
Re: Kleinempfänger with lots of hum
Hi,
I think you will find this is not mains hum at all, and has nothing to do with HT smoothing! I had exactly the same issue on the VE301W I've been working on. Yours sounds exactly the same. My 4 & 2 mfd caps tested perfectly and indeed there was not much ripple on the HT when viewed on a 'scope. Adding extra smoothing made no difference at all. The caps on the VE301 are not polarised. All the noise was being generated by the first valve. What was left of the metalising was not being grounded. Wrapping the valve in foil got rid of most of the hum and careful adjustment of the hum balancing pot got rid of nearly all the rest. The output valve, being directly heated, operates immediately. The first valve, having a cathode, takes a while to warm up. Mine hums loudly until the first valve starts to operate and then it quietens down. Also in mine, the 5 low value tubular capacitors needed replacing as they were very leaky. I don't have the DKE38 circuit to hand so I don't know how similar the circuit is to the VE301 so don't know how much of the above applies. Good luck All the best Nick |
13th Dec 2018, 3:25 am | #11 |
Hexode
Join Date: Aug 2010
Location: Malvern, Worcestershire, UK.
Posts: 347
|
Re: Kleinempfänger with lots of hum
Very different to your set Nick,the circuit is found easily by googling for it and it is AC/DC chassis with a combined valve comprising an indirectly heated triode detector/beam Tetrode output design,this valve is not metalised. There is the familiar high impedence speaker and no output transformer.
The smoothing caps really have to be the first items to exclude with certainty in order to narrow this down and corner the fault. I am sure posts no. 2,6 7 & 9 offer very good advice and would really help. One last thought before getting into bed after a very long day-make sure any workshop flourescent lights in the vicinity are switched off!!! you would not be the first person to experience this non fault hum Last edited by VT FUSE; 13th Dec 2018 at 3:41 am. Reason: Extra neuronal stirring |
13th Dec 2018, 11:36 am | #12 | |
Octode
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
|
Re: Kleinempfänger with lots of hum
Quote:
The two valves used must have had 55V heaters which must have been very unusual. I've heard the VY2 can suffer O/C heater. I still stand by my first sentence above though, I still don't think it's mains hum! (I'm very happy to be proved wrong- I often am!) It sounds more like the sound you get when you put your finger on the grid of a valve. The VCL11 valve would appear to be metalised, so could still be an issue. Your point about fluorescent lighting is good- that was causing me problems and it was a while before I thought to turn the light over the bench off! All the best Nick |
|
13th Dec 2018, 9:40 pm | #13 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Re: Kleinempfänger with lots of hum
I have checked polarity and it is fine. I just looked at the 0.9uF cap and from it both electrolytic caps are on the negative side so it is fine.
I still have hum. I have also got it running on 150v and the hum is the same. I have ordered a new VCL 11 tube...
__________________
EA3IAV |
14th Dec 2018, 8:51 am | #14 |
Tetrode
Join Date: Apr 2018
Location: Barcelona, Spain.
Posts: 62
|
Re: Kleinempfänger with lots of hum
I am having a look at the whole circuit and it is weird the connection made on a resistor. It is suspicious that there is a broken connection on the potentiometer
Can somebody confirm that the connection is fine where it is or it should be on the red spot ai show on the attachment?
__________________
EA3IAV |
14th Dec 2018, 11:16 am | #15 |
Heptode
Join Date: Feb 2010
Location: Duffort, Gers, France
Posts: 714
|
Re: Kleinempfänger with lots of hum
There were many different makers of these and every one did things a bit differently. However it should look roughly like this one. It looks to me that there is a wire missing on yours. BTW that's not a potentiometer, its a variable capacitor.
__________________
Stuart The golden age is always yesterday - Asa Briggs |
14th Dec 2018, 11:53 am | #16 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
|
Re: Kleinempfänger with lots of hum
The OP should compare the wiring of his set with the circuit diagram.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |