Tandberg 64x after changing capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

Levente · 25th Nov 2016, 8:14 pm

Hello tube gear lovers.

I have a tape recorder Tandberg including tubes such ECC81 ECC82 ECC83. On one of the pcb where I have one ECC81 and one ECC82 opposite each other does not lit up at all when I switch the unit on. Others are fine... the other ECC81 is the strongest, then the ECC83s and the other one of ECC82 is the weakest.

I was going through this unit and replaced all of the miniprint caps, the electrolyt caps too. Some of the small Siemens caps next to the tubes and what I have is weak sound on the left channel even though the eagle eye is full on, R channel eagle eye is barely responding and nearly no sound at all. Also no sound on playback...

Not sure where to go from here but if any of you could point me a direction I would really appreciate it.

Tubes are replaced and should be working fine...

Thanks for any advice, i just don't want to give up on this beauty!

radiotechnician · 29th Nov 2016, 9:11 am

Tubes in your machines are paired in series. If you have tested all the
tubes, and all were good, albeit weak, or not, then the pair not
lighted may have a crack in the print between the sockets, or at any
pin 4 or 5 termination.

If you cannot readily see any cracks, a DVM set to DC could be used to
trace the circuit with the power on. The circuit runs at 24 volts.

If you decide to do this, first remove the 0.2 A HT fuse. This will prevent
damage, should a probe slip. It also will be safer for you.

ricard · 29th Nov 2016, 9:42 am

My (fairly limited) experience with these machines is that leaky Miniprint (Rifa) caps can cause all sorts of weird problems. My advice would be to replace all the Miniprints you can find (with the possible exception of the ones on the indicator valve boards as they are really awkward to get at) and then retest the machine before doing anything else. One three of the four 64:s I've encountered this was enough to bring the machine up to spec. (Of course, you need to figure out any problems if the valves don't light up first, although with some valves it can be really hard to see them lighting up at all).

Levente · 29th Nov 2016, 7:01 pm

Thanks Radiotechnician...i will try my best. I had a look on one particular tube holder and if i move it around, it comes alive, sending signal to the opposite tube...the opposite tube lights up for a millisecond fully like a lightbulb and then goes back to a little lighting pins....kinda very light red color...

Hey Ricard....thanks again your reply. I have changed all the miniprints..thats was my first move....not sure what the problem is really...i was hoping that is the only problem with this but looks like no...maybe those Hunts paper caps for the bypass at the resistors... or maybe some resistors are also out...nothing else i can think of really...what the heck could be the problem, i am just guessing..

Thanks again for you both the help...could this be a resistor issue somewhere in the circuit?

Best,
Levente

radiotechnician · 30th Nov 2016, 1:23 pm

Some ECC83 tubes have a tendency to flash brightly on first
powering. It is harmless.

http://www.ebay.com/gds/Why-Mullard-...2972031/g.html

ricard · 30th Nov 2016, 3:39 pm

The contacts in the valve holders could have been damaged. I've come across a few where one arm of the fork that grips the valve pin had broken off, so that there was essentially no contact pressure. Wiggling the valve brought back temporary functionality.

Yes, there could be other capacitors, like the Hunts that have failed, although in these machines they are usually low value types and used in the equalizer circuitry so they affect the frequency response mostly. Another thing is as you say resistors, which can go high in value, especially composite anode resistors are prone to this, which lowers the anode current and the valve then isn't operating at its correct operating point.

Levente · 1st Dec 2016, 6:53 am

Thank you radiotechnician for the info and the link...the only one brighten up when gets energized is one of the ecc81 Tungsram but i guess it is the same principal. I will go ahead and change one or two suspicious looking tube holders maybe that will sort out the issue. If not, i need to find a faulty resistor which will be a big task with my "current technical knowledge"

Thanks again and have a wonderful day!

Hey Ricard,

Thank you. I think I will get that dodgy looking one changed and see if that will fox the issue...if not, i will need to find a faulty resistor. Not sure where to start tho...there are soo many of them and finding the measures of those old ones....i got confused which way you read them....from the silver sparkly side or the brown one...

Thanks again Ricard, and have a great day.

martiR2R · 1st Dec 2016, 5:56 pm

Re resistors, it doesn't matter which way round you connect your meter but it is advisable to desolder one end otherwise the reading could be affected by other components in the circuit.

Levente · 1st Dec 2016, 7:15 pm

Thanks guys again for your inputs. I have attached a picture of the the playback amplifier board. There are 3 tube holders where the pins 4 and 5 has no continuity measured with a voltmeter. Is this odd right? I believe these pins should have connections with each other.

I am not sure why is this happening, maybe this is also could be the problem source. Interesting!

Station X · 1st Dec 2016, 8:34 pm

Continuity is not measured with a voltmeter or with a DMM set to measure volts.

Are you saying that with the unit powered up and the valves plugged in, with your meter set to read volts, you are not measuring a voltage between pins 4 and 5 of the valveholders indicated?

Measure the DC voltage from chassis to pins 4 andd 5 of each vlveholder. Report the results here and someone will advise you.

Levente · 1st Dec 2016, 8:37 pm

Quote:

Originally Posted by Station X

Continuity is not measured with a voltmeter or with a DMM set to measure volts.

Are you saying that with the unit powered up and the valves plugged in, with your meter set to read volts, you are not measuring a voltage between pins 4 and 5 of the valveholders indicated?

Hi there. Thanks for the note. No I have set my multimeter to check continuity with the beep. 1 out of 4 is beeping at pin 4/5, the rest tube holders are not, that's why I thought there could be an issue.

Maybe I am completely wrong.

Station X · 1st Dec 2016, 9:02 pm

Depends what your meter sees as continuity. Valve heaters will always have some resistance and are not a short-circuit.

Another problem is that even if a valve's heater is open circuit, you may still see continuity, or a resistance, via a parallel path through the other heaters.

You can check the heaters by removing each valve in turn and measuring continuity (LOW RESISTANCE) between pins 4 and 5 of the valve.

To test the whole heater chain(s) it would be better to measure voltage.

Levente · 4th Dec 2016, 11:41 am

Thanks for the info. I have now changed the tube holder which had connection problems. Now the paralell tube also lights up. Still having the same problem. Very weak sound even tho the volume is full on. When I hit the record channel 1 and 2, the same weak sound and the magic eye indicator Left is not responding, the R one measures a full on max high volume (like in a peak)....

I read somewhere this is a phase reverse issue such:

This can be a bad 1/2 tube, a faulty socket contact, a broken or open plate resistor or coupling capacitor to the output tube, or a bad solder joint on any of these.

Thats all sounds good but which one is then...shall i change the coupling caps next to each resistors..or shall i change resistors? or am i still having a faulty tube?

I will measure the voltage this afternoon ...but .. runnig out of ideas and my knowledge on this is very limited...seems like a very complicated machinery to me...

Station X · 4th Dec 2016, 11:46 am

Can you confirm that ALL the valves now light up please.

If so the next step is to take voltage readings and compare the results with those in the service sheet.

Levente · 4th Dec 2016, 12:24 pm

Visually, yes....not sure how bright they should be, but the ecc83s and ecc82s has two little "dot" like on the their tops...the ecc81s are much much brighter...

Will measure the voltages this afternoon...i will measure against the ground i have in my flat..right?

So will use the ground from my electricity connector socket...

Station X · 4th Dec 2016, 12:26 pm

Voltages should be measured between the chassis of the unit and the valve pin being tested.

Set your meter to a suitable DC Volts range.

Levente · 4th Dec 2016, 12:30 pm

Thanks Graham. Will do. Shall I measure each pins of each valves just to see the measures? It will not exceed 250V range there right? As my voltmeter is only capable up too 250V...

Levente · 4th Dec 2016, 12:31 pm

just read your pervious message...and the answer is there...sorry...

Station X · 4th Dec 2016, 12:40 pm

Here's the circuit for the valve part of one channel. You'll need to take voltage measurements on both channels.

Valve pins number clockwise from the gap when looking at the underside of the Printed Circuit Board (PCB).

Measure pins 1,2,3,7 and 8.

There should be zero volts on pins 2 and 7 the control grids.

Levente · 4th Dec 2016, 1:37 pm

Hi Graham, here are my reading.

Staring with the playback preamp+cathod follower board:

Tube ECC83 #1

1: 273V (anode)
2:0 (grid)
3:0 (cathode)
4:0 (heater)
5:0 (heater)
6: varies..1400V, then 302 then 259V the steady 302V (anode)
7: 0 (grid)
8:0 (cathode)
9:0 (heater CT)

Tube ECC83 #2

1:256V
2+3+4+5= 0V
6: 252V
7: 253V
8: 0
9: 0

Tube ECC82 #1

1:275V
2+3+4= 0V
5: 35V
6: 296V
7+8+9= 0V

Tube ECC82 #2

1: 275V
2+3+4: 0V
5: 35V
6: 298
7+8+9= 0V

There record preamplifier and the record amplifier board

Tube ECC83 #1

1: 305V
2+3+4+5= 0V
6: 302V
7+8+9= 0V

Tube ECC83 #2

1:300V
2+3+4+5= 0V
6: 302V
7+8+9= 0V

Tube ECC81 #1

1: 309V
2+3+4= 0V
5: 35V
6: 315V
7+8+9= 0V

Tube ECC81 #2

1: 324/310 V
2+3+4= 0V
5: 35V
6: 315
7+8+9= 0V

I think there is something dodgy going on....

29th Nov 2016, 9:42 am	#3
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Tandberg 64x after changing capacitors My (fairly limited) experience with these machines is that leaky Miniprint (Rifa) caps can cause all sorts of weird problems. My advice would be to replace all the Miniprints you can find (with the possible exception of the ones on the indicator valve boards as they are really awkward to get at) and then retest the machine before doing anything else. One three of the four 64:s I've encountered this was enough to bring the machine up to spec. (Of course, you need to figure out any problems if the valves don't light up first, although with some valves it can be really hard to see them lighting up at all).

29th Nov 2016, 7:01 pm	#4
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Thanks Radiotechnician...i will try my best. I had a look on one particular tube holder and if i move it around, it comes alive, sending signal to the opposite tube...the opposite tube lights up for a millisecond fully like a lightbulb and then goes back to a little lighting pins....kinda very light red color... Hey Ricard....thanks again your reply. I have changed all the miniprints..thats was my first move....not sure what the problem is really...i was hoping that is the only problem with this but looks like no...maybe those Hunts paper caps for the bypass at the resistors... or maybe some resistors are also out...nothing else i can think of really...what the heck could be the problem, i am just guessing.. Thanks again for you both the help...could this be a resistor issue somewhere in the circuit? Best, Levente

30th Nov 2016, 1:23 pm	#5
radiotechnician Pentode Join Date: Jan 2013 Location: Powell River, British Columbia, Canada. Posts: 217	Re: Tandberg 64x after changing capacitors Some ECC83 tubes have a tendency to flash brightly on first powering. It is harmless. http://www.ebay.com/gds/Why-Mullard-...2972031/g.html __________________ Steve Dow VE7ASO

30th Nov 2016, 3:39 pm	#6
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Tandberg 64x after changing capacitors The contacts in the valve holders could have been damaged. I've come across a few where one arm of the fork that grips the valve pin had broken off, so that there was essentially no contact pressure. Wiggling the valve brought back temporary functionality. Yes, there could be other capacitors, like the Hunts that have failed, although in these machines they are usually low value types and used in the equalizer circuitry so they affect the frequency response mostly. Another thing is as you say resistors, which can go high in value, especially composite anode resistors are prone to this, which lowers the anode current and the valve then isn't operating at its correct operating point.

1st Dec 2016, 5:56 pm	#8
martiR2R Hexode Join Date: Aug 2012 Location: Preston, Lancashire, UK. Posts: 343	Re: Tandberg 64x after changing capacitors Re resistors, it doesn't matter which way round you connect your meter but it is advisable to desolder one end otherwise the reading could be affected by other components in the circuit. __________________ BVWS Member (lapsed!)

29th Nov 2016, 9:11 am	#2
radiotechnician Pentode Join Date: Jan 2013 Location: Powell River, British Columbia, Canada. Posts: 217	Re: Tandberg 64x after changing capacitors Tubes in your machines are paired in series. If you have tested all the tubes, and all were good, albeit weak, or not, then the pair not lighted may have a crack in the print between the sockets, or at any pin 4 or 5 termination. If you cannot readily see any cracks, a DVM set to DC could be used to trace the circuit with the power on. The circuit runs at 24 volts. If you decide to do this, first remove the 0.2 A HT fuse. This will prevent damage, should a probe slip. It also will be safer for you. __________________ Steve Dow VE7ASO

1st Dec 2016, 6:53 am	#7
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Thank you radiotechnician for the info and the link...the only one brighten up when gets energized is one of the ecc81 Tungsram but i guess it is the same principal. I will go ahead and change one or two suspicious looking tube holders maybe that will sort out the issue. If not, i need to find a faulty resistor which will be a big task with my "current technical knowledge" Thanks again and have a wonderful day! Hey Ricard, Thank you. I think I will get that dodgy looking one changed and see if that will fox the issue...if not, i will need to find a faulty resistor. Not sure where to start tho...there are soo many of them and finding the measures of those old ones....i got confused which way you read them....from the silver sparkly side or the brown one... Thanks again Ricard, and have a great day.

1st Dec 2016, 7:15 pm	#9
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Thanks guys again for your inputs. I have attached a picture of the the playback amplifier board. There are 3 tube holders where the pins 4 and 5 has no continuity measured with a voltmeter. Is this odd right? I believe these pins should have connections with each other. I am not sure why is this happening, maybe this is also could be the problem source. Interesting! Attached Thumbnails

1st Dec 2016, 8:34 pm	#10
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Tandberg 64x after changing capacitors Continuity is not measured with a voltmeter or with a DMM set to measure volts. Are you saying that with the unit powered up and the valves plugged in, with your meter set to read volts, you are not measuring a voltage between pins 4 and 5 of the valveholders indicated? Measure the DC voltage from chassis to pins 4 andd 5 of each vlveholder. Report the results here and someone will advise you. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

1st Dec 2016, 9:02 pm	#12
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Tandberg 64x after changing capacitors Depends what your meter sees as continuity. Valve heaters will always have some resistance and are not a short-circuit. Another problem is that even if a valve's heater is open circuit, you may still see continuity, or a resistance, via a parallel path through the other heaters. You can check the heaters by removing each valve in turn and measuring continuity (LOW RESISTANCE) between pins 4 and 5 of the valve. To test the whole heater chain(s) it would be better to measure voltage. Attached Thumbnails __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Dec 2016, 11:41 am	#13
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Thanks for the info. I have now changed the tube holder which had connection problems. Now the paralell tube also lights up. Still having the same problem. Very weak sound even tho the volume is full on. When I hit the record channel 1 and 2, the same weak sound and the magic eye indicator Left is not responding, the R one measures a full on max high volume (like in a peak).... I read somewhere this is a phase reverse issue such: This can be a bad 1/2 tube, a faulty socket contact, a broken or open plate resistor or coupling capacitor to the output tube, or a bad solder joint on any of these. Thats all sounds good but which one is then...shall i change the coupling caps next to each resistors..or shall i change resistors? or am i still having a faulty tube? I will measure the voltage this afternoon ...but .. runnig out of ideas and my knowledge on this is very limited...seems like a very complicated machinery to me...

4th Dec 2016, 11:46 am	#14
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Tandberg 64x after changing capacitors Can you confirm that ALL the valves now light up please. If so the next step is to take voltage readings and compare the results with those in the service sheet. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Dec 2016, 12:24 pm	#15
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Visually, yes....not sure how bright they should be, but the ecc83s and ecc82s has two little "dot" like on the their tops...the ecc81s are much much brighter... Will measure the voltages this afternoon...i will measure against the ground i have in my flat..right? So will use the ground from my electricity connector socket...

4th Dec 2016, 12:26 pm	#16
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Tandberg 64x after changing capacitors Voltages should be measured between the chassis of the unit and the valve pin being tested. Set your meter to a suitable DC Volts range. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Dec 2016, 12:30 pm	#17
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Thanks Graham. Will do. Shall I measure each pins of each valves just to see the measures? It will not exceed 250V range there right? As my voltmeter is only capable up too 250V...

4th Dec 2016, 12:31 pm	#18
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors just read your pervious message...and the answer is there...sorry...

4th Dec 2016, 12:40 pm	#19
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Tandberg 64x after changing capacitors Here's the circuit for the valve part of one channel. You'll need to take voltage measurements on both channels. Valve pins number clockwise from the gap when looking at the underside of the Printed Circuit Board (PCB). Measure pins 1,2,3,7 and 8. There should be zero volts on pins 2 and 7 the control grids. Attached Thumbnails __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Dec 2016, 1:37 pm	#20
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tandberg 64x after changing capacitors Hi Graham, here are my reading. Staring with the playback preamp+cathod follower board: Tube ECC83 #1 1: 273V (anode) 2:0 (grid) 3:0 (cathode) 4:0 (heater) 5:0 (heater) 6: varies..1400V, then 302 then 259V the steady 302V (anode) 7: 0 (grid) 8:0 (cathode) 9:0 (heater CT) Tube ECC83 #2 1:256V 2+3+4+5= 0V 6: 252V 7: 253V 8: 0 9: 0 Tube ECC82 #1 1:275V 2+3+4= 0V 5: 35V 6: 296V 7+8+9= 0V Tube ECC82 #2 1: 275V 2+3+4: 0V 5: 35V 6: 298 7+8+9= 0V There record preamplifier and the record amplifier board Tube ECC83 #1 1: 305V 2+3+4+5= 0V 6: 302V 7+8+9= 0V Tube ECC83 #2 1:300V 2+3+4+5= 0V 6: 302V 7+8+9= 0V Tube ECC81 #1 1: 309V 2+3+4= 0V 5: 35V 6: 315V 7+8+9= 0V Tube ECC81 #2 1: 324/310 V 2+3+4= 0V 5: 35V 6: 315 7+8+9= 0V I think there is something dodgy going on....