Tandberg TP41; internal access and squeal problems. - UK Vintage Radio Repair and Restoration Discussion Forum

radiogammon · 3rd Jan 2007, 6:38 pm

I have just taken delivery of a Tandberg TP41 transistor set in reasonable condition. I had been looking for one of these for some time and got it from a seller in Sweden. It appears to work fine on FM and sounds great apart from some cabinet vibration which. On MW, however, it tends to squeal as you move the pointer across the band and will also squeal when tuned into strong local stations. I suspect some of the electrolytics may need changing but any other suggestions welcome. Also, has anyone any experience in removing the case to get at the chassis. It doesn't look particularly obvious.

Chris_C · 3rd Jan 2007, 7:33 pm

Hi John,

I had one of these many years ago. If I remember right you have to remove the handle first then the case slides off from the bottom.

Again if memory serves correctly some of the resistors had radial leads.

Hope this helps but I'm not 100% hopefully others may have more uptodate information.

Cheers

Nickthedentist · 3rd Jan 2007, 8:11 pm

John,

Be CAREFUL!!!

I bought one of these and managed to completely mess it up whilst trying to remove the case in what I thought was the obvious way.

It DID come off, but with a sudden jerk, snapping off the tuning knob's shaft and pulley from the plastic chassis, and pulling the dial cord off for good measure. Give me a Hacker Sovereign any day.

I was so fed up with the thing by that stage that I donated it to Paul Sherwin, so if he hasn't chucked it, maybe he could examine the bits and work out the PROPER way to do it (I suspect not taking the knobs off first was my main mistake).

They look like lovely radios to me, though I understand the OP stage is prone to burn-up, leading to the demise of the LS (the cone on mine was completely seized, apparently due to a fried voicecoil).

Nick.

paulsherwin · 3rd Jan 2007, 8:19 pm

Quote:

Originally Posted by Nickthedentist

I was so fed up with the thing by that stage that I donated it to Paul Sherwin, so if he hasn't chucked it, maybe he could examine the bits and work out the PROPER way to do it (I suspect not taking the knobs off first was my main mistake).

It's sitting on a shelf in front of me as I type, untouched since I acquired it. It's some way down the 'to do' list, but if John is doing one it's a good time for me to have a look at it, so maybe I'll bump it up

Paul

radiogammon · 3rd Jan 2007, 9:55 pm

Quote:

Originally Posted by paulsherwin

It's sitting on a shelf in front of me as I type, untouched since I acquired it. It's some way down the 'to do' list, but if John is doing one it's a good time for me to have a look at it, so maybe I'll bump it up

Paul

Thanks, Paul. I think it should be worth it as everyone says they sound great when working properly (as good as Hackers?). Mine certainly sounds good on FM but has a problem with squealing on AM.They have a large speaker (about 8x5 I think) and with bass and treble controls. Can you see how the case should be taken apart?

Nickthedentist · 3rd Jan 2007, 9:57 pm

Quote:

Originally Posted by radiogammon

Can you see how the case should be taken apart?

I think that there are two metal strips on the side of the cabinet which hold the two wooden halves together. Removing these then allows the wooden covers to be separated from one another, thus exposing the chassis and speaker.

Well, probably

The top plate and chassis do NOT simply slide up and out of the wooden case, as I originally suspected.

Nick.

paulsherwin · 3rd Jan 2007, 11:05 pm

Quote:

Originally Posted by Nickthedentist

I think that there are two metal strips on the side of the cabinet which hold the two wooden halves together. Removing these then allows the wooden covers to be separated from one another, thus exposing the chassis and speaker.

Nick is correct. Remove the 2 handle screws and associated plastic bushes and lift the handle away. The 2 aluminium strips can then be removed and the 2 wooden halves will separate.

Incidentally, the 2 handle screws on mine look 'wrong' somehow, as if there was originally some additional plastic trim - any comments Nick?

Paul

radiogammon · 3rd Jan 2007, 11:58 pm

Thanks Paul and Nick. Have the case separated . The speaker is in fact a 9x5 - practically the full width of the case. I will remove it tomorrow to get at the components on the PCB.

Nickthedentist · 4th Jan 2007, 9:21 am

Quote:

Originally Posted by paulsherwin

Incidentally, the 2 handle screws on mine look 'wrong' somehow, as if there was originally some additional plastic trim - any comments Nick?

Sorry, no. It's as-received (apart from the damage I inflicted on it

).

Nick.

radiogammon · 4th Jan 2007, 7:44 pm

Well, I removed the speaker and had a look around the components on the PCB. One component, covered by a clear plastic sleeve didn't look normal, as it appeared to have a greenish powder leaking from one end underneath the sleeve (see photo). I had no idea what this was, but after doing some searching on the net, I found a forum in Norway which had discussions on the TP41 problems.

Unfortunately the language was Norwegian, but I managed to get enough words translated to understand that it is a low voltage stabilizer to provide 1.5V to part of the circuit. It is referred to as a stabistor and apparently doesn't last more than a few years. I hooked up a 12V power supply and the voltage across the stabistor was nearer 5v rather than 1.5V.

The recommended replacement (as used in the later TP43 model) was two 1N4148 and one AA119 diode in series with a 220uf cap across them. As I didn't have these particular diodes in my kit, I rigged up a pair of 1N4001's and an OA79 and tried them.

These gave me around 1.7V and I also found the squealing had now stopped on AM, so it looks as if this is where the problem lies. I have now ordered a few of the recommended diodes from an eBay shop and will fit these when they arrive. Hopefully this will give me a permanent cure, if I can ever manage to put the case together again. Will keep you posted.

paulsherwin · 4th Jan 2007, 7:49 pm

Quote:

Originally Posted by radiogammon

I have now ordered a few of the recommended diodes from an eBay shop and will fit these when they arrive.

You just need to find a diode combination which will strike at 1.5V. If like me you have a junk box full of scavenged diodes, it's an easy matter to go through them with a DMM set to the diode test function and measure the voltage drop. Typical rectifiers will drop 0.5-0.8V, germaniums and Schottkys much less.

Congratulations on sorting your fault out - I suspect I'll have rather more to deal with when I get round to mine

Paul

3rd Jan 2007, 6:38 pm	#1
radiogammon Retired Dormant Member Join Date: Dec 2002 Location: County Down, Northern Ireland, UK. Posts: 275	Tandberg TP41; internal access and squeal problems. I have just taken delivery of a Tandberg TP41 transistor set in reasonable condition. I had been looking for one of these for some time and got it from a seller in Sweden. It appears to work fine on FM and sounds great apart from some cabinet vibration which. On MW, however, it tends to squeal as you move the pointer across the band and will also squeal when tuned into strong local stations. I suspect some of the electrolytics may need changing but any other suggestions welcome. Also, has anyone any experience in removing the case to get at the chassis. It doesn't look particularly obvious. Attached Thumbnails

3rd Jan 2007, 7:33 pm	#2
Chris_C Hexode Join Date: Jan 2003 Location: Darlington (DL3) North East U.K. Posts: 394	Re: Tandberg TP41 Hi John, I had one of these many years ago. If I remember right you have to remove the handle first then the case slides off from the bottom. Again if memory serves correctly some of the resistors had radial leads. Hope this helps but I'm not 100% hopefully others may have more uptodate information. Cheers __________________ Chris C G8TJR

3rd Jan 2007, 8:11 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,844	Re: Tandberg TP41 John, Be CAREFUL!!! I bought one of these and managed to completely mess it up whilst trying to remove the case in what I thought was the obvious way. It DID come off, but with a sudden jerk, snapping off the tuning knob's shaft and pulley from the plastic chassis, and pulling the dial cord off for good measure. Give me a Hacker Sovereign any day. I was so fed up with the thing by that stage that I donated it to Paul Sherwin, so if he hasn't chucked it, maybe he could examine the bits and work out the PROPER way to do it (I suspect not taking the knobs off first was my main mistake). They look like lovely radios to me, though I understand the OP stage is prone to burn-up, leading to the demise of the LS (the cone on mine was completely seized, apparently due to a fried voicecoil). Nick. Last edited by Darren-UK; 6th Aug 2007 at 11:36 pm. Reason: Excessive use of emoticons.

3rd Jan 2007, 11:58 pm	#8
radiogammon Retired Dormant Member Join Date: Dec 2002 Location: County Down, Northern Ireland, UK. Posts: 275	Re: Tandberg TP41 Thanks Paul and Nick. Have the case separated . The speaker is in fact a 9x5 - practically the full width of the case. I will remove it tomorrow to get at the components on the PCB.

4th Jan 2007, 7:44 pm	#10
radiogammon Retired Dormant Member Join Date: Dec 2002 Location: County Down, Northern Ireland, UK. Posts: 275	Re: Tandberg TP41 Well, I removed the speaker and had a look around the components on the PCB. One component, covered by a clear plastic sleeve didn't look normal, as it appeared to have a greenish powder leaking from one end underneath the sleeve (see photo). I had no idea what this was, but after doing some searching on the net, I found a forum in Norway which had discussions on the TP41 problems. Unfortunately the language was Norwegian, but I managed to get enough words translated to understand that it is a low voltage stabilizer to provide 1.5V to part of the circuit. It is referred to as a stabistor and apparently doesn't last more than a few years. I hooked up a 12V power supply and the voltage across the stabistor was nearer 5v rather than 1.5V. The recommended replacement (as used in the later TP43 model) was two 1N4148 and one AA119 diode in series with a 220uf cap across them. As I didn't have these particular diodes in my kit, I rigged up a pair of 1N4001's and an OA79 and tried them. These gave me around 1.7V and I also found the squealing had now stopped on AM, so it looks as if this is where the problem lies. I have now ordered a few of the recommended diodes from an eBay shop and will fit these when they arrive. Hopefully this will give me a permanent cure, if I can ever manage to put the case together again. Will keep you posted. Attached Thumbnails Last edited by Darren-UK; 6th Aug 2007 at 11:34 pm. Reason: Paragraphed.