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Old 21st Feb 2017, 12:27 pm   #121
'LIVEWIRE?'
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Default Re: Tandberg Huldra 8 valve failure

You're right, Lee. It's just that most, if not all Ex8xx series valves have B9A (9 pin) bases
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Old 22nd Feb 2017, 2:51 am   #122
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Default Re: Tandberg Huldra 8 valve failure

Quote:
Originally Posted by Hunts smoothing bomb View Post
Measure the voltage by setting the meter to ACV and placing one probe in pin 4 socket and the other probe in the pin 5 socket.

You should have heater supply around 6 to 6.5vac
hopefully i am reading this it shows 3.21vac for the EF89 valve socket

Clive
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Old 22nd Feb 2017, 3:03 am   #123
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Default Re: Tandberg Huldra 8 valve failure

Quote:
Originally Posted by PJL View Post
Can you confirm there is no sound even in Gram and AM, and in FM that the magic eye is responding to tuning. If so, the EF89 is not your problem. The fault now lies with the audio section. I have a German user manual but that's not much use to me, and the switching is very complex.

1. Check the tape button is not depressed as it probably passes the audio through the tape input/output.

2. Check the speaker selection switch.

3. Switch to Gram and turn up the volume. Is there any hiss or hum? Do you get any clicking sounds when switching between gram and other sources?

1 i have checked the tape switch and it is defiantly not switched on

2 speaker switch which is on the front tried all the settings nothing

3. same results for gramophone no static or audio hiss. when it was running i only had the FM and AM(MB) running and all the different speaker connections worked.
the frustrating part is not been able to read the service manual, i have done most of translation if anyone want to look at it, i will email it along with the original one.

Clive
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Old 22nd Feb 2017, 7:50 am   #124
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Default Re: Tandberg Huldra 8 valve failure

Right, now go over the whole PCB/chassis particularly the transistorised audio stage and look for a burn, blown component, melted track etc particularly in the area where a flash would of reflected in the tuning eye.

If there was a flash could it have been just the fuse going? Is it inline light wise with the eye?

Something went pop, it will have left a trace behind, find it and we are getting somewhere.
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Old 22nd Feb 2017, 9:51 am   #125
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Default Re: Tandberg Huldra 8 valve failure

There is a 2.2A fuse in the LT secondary. Hopefully, just the fuse will have blown from the flyback surge created by the HT fault. Replace the fuse, leave the lamp limiter in place, switch on and measure the LT volts across the reservoir C701.

Attachment 134675

Last edited by Station X; 22nd Feb 2017 at 10:24 am. Reason: Circuit added.
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Old 22nd Feb 2017, 10:05 am   #126
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Default Re: Tandberg Huldra 8 valve failure

Anyone noticed post#122 yet...

Lawrence.
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Old 22nd Feb 2017, 10:39 am   #127
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Default Re: Tandberg Huldra 8 valve failure

As frustrating as this is, anyone else think it might be a good idea to check the other valves heater voltages ?
I just don't see how it can be almost exactly half the voltage it should be when all the heaters are all powered the same.

Also have the "sikringslampe" translated to "security lamps" 12v 18watt on the Transistor feeds been checked yet ? my guess is they light if there is a fault but if one is faulty itself ?
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Last edited by Freya; 22nd Feb 2017 at 11:02 am.
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Old 22nd Feb 2017, 11:03 am   #128
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Default Re: Tandberg Huldra 8 valve failure

I can see how the measured heater voltage could be half of what it should be, defective valve holder contacts, dry joint, cracked print circuit etc. Or defective meter.

Lawrence.

Last edited by ms660; 22nd Feb 2017 at 11:07 am. Reason: addittion
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Old 22nd Feb 2017, 7:40 pm   #129
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Default Re: Tandberg Huldra 8 valve failure

Despite strong evidence that the EF89 is working, the measurement looks wrong, however, the fault is no audio at all and this is definitely not directly related to the EF89.

It would be useful to know if we are looking at a faulty meter or possibly a damaged mains transformer so let's get side-lined from tracking down the amplifier fault and make a few checks first:

1. What is the AC input voltage setting now?
2. Are you using a lamp limiter?
3. Measure the AC voltages on the secondaries of the mains transformer (see attached). Be careful as there are high voltages on the transformer.
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Old 23rd Feb 2017, 1:04 am   #130
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Default Re: Tandberg Huldra 8 valve failure

This is the list of fuses, so far i have only checked and replaced S3
8.2.6 Fuses

Ref. no. Type Remarks
S.H.8 2000 m.A, mites. slow Pl. no. 19408, Wickmann
S2 H8 6. A PI, no. 1957 7, Wickmann
S3 H8 160 mA, slow 30 x 5 mm PI. no. 19197, Wickmann
S4 H8 Thermal fuse, secure. metal 1:12 C
S5-H8 Fuse Lamp, 12 V, 18 W. Osram, no. 6475
S5-H8 Sikringsla mpe, 12 V, 18 W, Osram no. 6475
R2Al-H8 Skringsmotstand kohm 10% 2.5 W 16038 T previously used Vitrohm 16025 T

i am going to check the others, which i haven't done up to now. as far as the lamp limiter, it hasn't been in use for the last few checks, and remains off. the set is currently running in the 115v position. and last i am going to check the transformer reading
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Old 23rd Feb 2017, 5:23 am   #131
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Default Re: Tandberg Huldra 8 valve failure

here are some readings. when i checked on of the fuses one was no good, located below the one that blew originally. this is listed on the schematic as S1 see diagram, would that have something to do with my current issue no audio

NOTE the readings in these pictures is with the fuse that is blown and removed

that fuse is S1 H.8 2000 m.A, mites. slow Pl. no. 19408, Wickmann., i will have to order one

Clive
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Old 23rd Feb 2017, 8:36 am   #132
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Default Re: Tandberg Huldra 8 valve failure

You might want more than one !
Glad we are on the right track yesterday with the transistor feeds not being powered, we are getting somewhere at last.
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Old 23rd Feb 2017, 9:49 am   #133
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Default Re: Tandberg Huldra 8 valve failure

With S1 blown there will be no 24v(DC) supply, so D701, C11 and associated components need checking, and, since the +24v presumably supplies the transistorised audio amplifier circuit, this needs checking, too.
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Old 23rd Feb 2017, 10:28 am   #134
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Default Re: Tandberg Huldra 8 valve failure

Looking back, it started with S3 failing, which drives the HT to the Valves, now we find S1 has also failed at some point, this provides the +33 volts DC to the Transistors.
This sounds odd to me that both AC fuses would be gone, my feeling is an incorrect input voltage could have caused both of these to fail.

I will take a back seat now and let the brighter members continue.
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Old 23rd Feb 2017, 12:36 pm   #135
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Default Re: Tandberg Huldra 8 valve failure

When the HT was shorted and the fuse failed, it is quite possible that there would have been a large transient from the mains transformer although I am surprised it would have been enough to take out a slow blow fuse. The voltage readings don't make much sense although the ones on the left will be the AC input and will be floating. I would have liked to have seen the 6.3V AC reading.

As Freya has said, don't just buy one fuse! If it has caused faults in the transistor amplifiers the fuse will blow again.

An option to save a fuse is to power the radio through a lamp limiter and clip your meter on the 10A current position as a replacement for the 2A fuse. It must be on a lamp limiter or you might otherwise damage the meter.

If the current is much above 1A switch off quickly as it is likely there is a fault in the transistor amplifier, otherwise, it may work but probably not too well. You can then remove the meter and lamp limiter, insert a new fuse and hopefully it will be working again.

If the current is much above 1A then we will need to fault trace the amplifiers.
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Old 23rd Feb 2017, 2:12 pm   #136
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Default Re: Tandberg Huldra 8 valve failure

To correct an error in my post # 133 above. The 24v in the circuit diagram is of course AC. As others have said, the DC Voltage at the filter capacitor C11 will be of the order of 33 to 34V when the fault(s) are repaired. That error aside, the remarks in my earlier post still apply. If either of the two 12v 18W bulbs in series with the supply lines from D701 have failed this may point to fault(s) downstream of the rectifier
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Old 24th Feb 2017, 1:07 am   #137
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Default Re: Tandberg Huldra 8 valve failure

forgot to include this yesterday, but maybe a moot point until i replace the fuse.
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Old 24th Feb 2017, 8:08 pm   #138
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Default Re: Tandberg Huldra 8 valve failure

You can use the meter and a lamp limiter to continue fault finding.
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Old 25th Feb 2017, 12:19 am   #139
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Default Re: Tandberg Huldra 8 valve failure

I just bought a new meter with better features from my old one should help and i will proceed to check the areas of interest.
Clive
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Old 25th Feb 2017, 3:02 am   #140
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Default Re: Tandberg Huldra 8 valve failure

Quote:
Originally Posted by roverp6 View Post
forgot to include this yesterday, but maybe a moot point until i replace the fuse.
Where was the black probe connected?

If to the other pole of the mains supply, the readings are around half what's expected.

If to the chassis, that is an incorrect measurement technique, but suggest there is no gross leakage between the transformer's primary and chassis, but the readings are best ignored for now.
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