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Old 27th Sep 2021, 7:59 am   #101
Heatercathodeshort
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Default Re: B&O Capri 606 TV (17") restoration

just a few thoughts. The fact that the EHT is now dropping appears to point to a fault in the LOPT. Is it possible that there is a tiny discharge from the positive side of the EHT rectifier to chassis? In my recent case with a KB PVP20 receiver, the EHT rectifier heater winding [just one turn] was building up a static charge and discharging to the core of the transformer.
This was not the violent discharge obtained with the total breakdown of the winding and could only be seen in total darkness as a very small discharge, more of an intermittent 'tick' producing the results you are experiencing. Replacing the winding produced a complete cure.
I presume the chassis uses a valve EHT rectifier such as the DY86/EY86 type.
John.
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Old 28th Sep 2021, 10:28 am   #102
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Default Re: B&O Capri 606 TV (17") restoration

Hi John,
Thanks you, yes it is a PL36/PY88/DY86 or DY87 affair. I will get back to check up on this within a few weeks, but I have not observed even the tiniest sparking/discharge from the EHT section at all, but I do see slight discoloration of the yellow protection sleeve where it makes contract with the line output winding.
I'm a bit in doubt about the "bubbly" appearance of the LOPT in general, as if it has been boiling hot at some point in time (see image). Maybe it is what they looked like from the factory. Unfortunately, the previous owner of the chassis said that it "did work", meaning that it would likely have been powered on with all the bad capacitors (!).

The EHT winding resistance measures about 98 ohms, and am sure it has measured about 112-115 ohm earlier after it was powered with a DC supply to driver out any moisture. I guess I could try this again, but it may be too late.

The 23" Capri (AW59-90) was using the AT2021 and according to the two schematics I have, the AT2018 and AT2021 are interchangeable. The EHT coil is encapsulated in white resin on the AT2021 and is what my Capri 606 came with, replacing the AT2016 which might have been unreliable.

The AT2021 I have, measures 115 Ohm on the EHT - that's about 17% higher. I assume that would make the EHT also rise by 17%, or to nearly 15 kV (?). But, according to this thread (in German) https://www.dampfradioforum.de/viewt...p?f=36&t=12342 , the resistance should be 200 Ohm - but not sure what to think.

I'm not sure how one would go about driving moisture out of these resin/plastic encapsulated EHT coils, or if it is even required.

No matter what, I'll test some more on the AT2018 and if all else fails, hopefully I can find someone who can rewind it.

Kind regards,
Troels
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Old 28th Sep 2021, 10:45 am   #103
German Dalek
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
Don`t worry about the "bubbly" LOPT! Thats only a result of the production
procedure.
Get rid of moisture in the kitchen oven, use 40°C and bake about an hour or longer.
Under normal circumstances this had to be done before.

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Old 13th Oct 2021, 12:01 pm   #104
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Default Re: B&O Capri 606 TV (17") restoration

Hi,

I gave the AT2018 a good drying out in the oven at 40-45 deg C. for many hours. Measurements are exactly the same on all tags.

Did the same with the AT2021 - and fitted this into the set instead, noting the change in tags. Would you believe it - STILL low-ish EHT, the same as with the AT2018.

It also seems that it isn't a perfect match with the scanning coils, as I now have a little bit of brightness "ringing" at the leftmost side. I reused the 220nF capacitor that the AT2018 used, as I don't have a 180nF available, that the AT2021 schematic lists - but this might correct the bad matching (?).

I'm really struggling to determine why the EHT is low and what exactly determines what the EHT will be. The DY87 is fine. Should I try a new PY88 or PL36? I suppose that if the line drive to the PL36 does not have enough amplitude (150V peaks), the EHT will become lower as well. With neither of the LOPTs I hear a clear line whistle, but I know the AT2021 in the old chassis did make quite an audible whistle.
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Old 14th Oct 2021, 2:04 pm   #105
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
Changing valves from a set which works perfectly has to be the first option.
Please remember, that there are caps & resistors which measured fine when cold or not under power!
Please remember the Vitrohm resistors, they were big in America and at Philips.
They are getting high in resistance in dozens inside a TV set!!
Use only the best caps in line output stages.
Good luck!
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Old 15th Oct 2021, 2:06 pm   #106
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Default Re: B&O Capri 606 TV (17") restoration

Thanks, German Dalek.

I didn't suspect the resistors in the LOPT section - they are extremely hard to get to (look up from the underside) and looked "fresh" and "pristine" - see attached image.
However, when de-soldering the resistors, for example the 10MOhm measures 12.2Mohm, and the 4.7MOhm from the boost cap tagged onto section f measures 6.1 MOhm. I have now ordered the full selection of resistors in this section along with a 0.18uF PP capacitor. Hopefully, 1W carbon-film Xicon resistors with a 500V rating are a suitable replacement (thinking of arc-over).

Who is the manufacturer of the red resistors in the photo? It looks similar to Beyschlag, but the ends seem more rounded.
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Old 18th Oct 2021, 11:24 am   #107
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Default Re: B&O Capri 606 TV (17") restoration

Hi!
They are made by Rosenthal. They are not too bad, but anyway, just all high value resistors are critical after so many years.
Good luck!

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Old 20th Oct 2021, 9:15 pm   #108
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Default Re: B&O Capri 606 TV (17") restoration

Ok, all Rosenthal resistors in the LOPT section replaced - all that were off value or questionable at least. Result: EHT still at 12.8 kV!

As I understand it, the EHT is directly related to the output of the PL36 anode, and nothing else. Please correct me if I'm wrong.

I measured the waveform of the line drive is just as it should be 160Vpp amplitude (should just be 150Vpp). Shape is perfect.
Measuring directly at g1 of PL36: -49Vdc, which is right on target. g2 is 164Vdc, 14V higher than the measurements on the schematic say, but I suppose that is fine as well.

Any other suggestions, anyone? The DY87 is glowing, but faintly/muted only.
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Old 21st Oct 2021, 5:57 am   #109
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
This post is going longer and longer.....
I don`t remember where all the issues came from.
Are you sure that your HV-probe is right? Did you tested it
with another working TV?
Your last picture is showing the faulty resistors - and the new? caps?

IT HAS TO BE CLEAR, that you have to use only the finest caps (Quality)
in HV/line output stages!
Now there are caps available which are only good for 50 Hz against distortion.
There are caps which doesn`t could deal with hight peak to peak voltages.

There is another problem with metal film resistors. Depending on the production
they are not able to work with higher voltages!
Some deflection coils covering resistors, very often in units for 70° and 90° angles.
Some companies did use awful thin wires for the wiring, I should swap them.

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Old 21st Oct 2021, 6:33 pm   #110
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Default Re: B&O Capri 606 TV (17") restoration

Thanks for your patience and bearing with me, German Dalek.
I haven't had time to take photos yet, however, I think there actually may be no problem, but I think I have forgotten all about how much old TVs actually overscan.

What I had done was to adjust picture width, so that it fitted with the supplied video signal.

I now instead adjusted the width potentiometer to the middle (~1 MOhm) and noticed a much clearer line whistle, and the height had shrunk a bit. This was easy to adjust, as the height potentiometer had plenty of headroom. Now, the EHT is about 14.5 kV. Increasing the width further makes it go to 15.5 kV, but of course, higher widths stresses the PL36 further.

I'm very aware of the quality of the components and usually order the best parts I can find from Mouser. The 0.18uF is Cornell Dubilier series 930 and the 0.1uF is series 940. The 56n boost cap was sourced locally: Wima FKP1 series.

I now feel very embarrassed of this, but afterall, it feels good that the much out of tolerance resistors were replaced.
Now, I'll work on getting it all "shined up" again, and will post a few demonstrations. Seem to remember someone was curious on the sound performance.
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Old 23rd Oct 2021, 10:32 am   #111
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Default Re: B&O Capri 606 TV (17") restoration

The Cornell Dublier 930 series isn't particularly suited for pulse applications. I don't know where it is in the circuit, so it might be fine but if it carries a substantial current you might want to use a 940 or FKP1 if you plan on using the TV regularly.
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Old 23rd Oct 2021, 11:29 am   #112
staticmind
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Default Re: B&O Capri 606 TV (17") restoration

Hi Maarten,
I have attached a few images showing where it is in the circuit. It's in series with the horizontal scan coil. Originally, B&O used a Philips green/mustard cap rated at 125Vdc. I don't understand that when the waveform shows up to 475V pulses at line frequency, but perhaps the pulse toleration of these old capacitors was better (?).

As you see, I don't have a lot of space, and it is best if it could be a axial type (for rigidity). It can't be too tall either, as the rectifier tube base also takes up space. As an180nF is a bit rare. I can find a NOS 1500V rated 180nF as an alternative, but no other specifications.

By the way: The Xicon resistors that replaced the Rosenthals are shown in the last picture along with two 220k PR02 (Xicons out of stock). Should I rather have gone for special resistors that were rated for high voltages, such as the OSP10 from EBG Resistors? Those are rated for 1000V continously, while the Xicons are 500V and 1000V for short periods. (Data sheet: https://www.mouser.dk/datasheet/2/35...35-1893446.pdf ). It seems a bit "off" having to contact a specialist company in order to obtain the the "right" resistors for the job.
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Old Yesterday, 5:25 am   #113
German Dalek
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
Just the lousiest resistor of all, the Vitrohm is not changed! Just they are big trouble makers.
I cannot say something about the quality of your new caps.
What is inside the hose? Sometimes there are resisitors hidden, only to save them from being shorten by other parts.

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Old Yesterday, 7:56 am   #114
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Default Re: B&O Capri 606 TV (17") restoration

Hi,
I assume you mean the resistor under the yellow wire? Well, it measured spot on, but I'll change it then
The thing is that there are tons of Vitrohms in this set, and only replaced those out of tolerance - but if there are issues, they are of course likely subject to be replaced.
The hose contains a shielded (steel wrapped) cable going towards the PL36 (and the 220k Vitrohm mounted on the backside of the PL36 base.. yes, I know).

Regarding capacitors:
For the boost cap, I replaced the CDE 940 with the Wima FKP1 because I prefer to have the stated 56n compared to 47n. Unfortunately, a CDE 940 (or similar) 10 nF is out of stock for a long time, so not possible to parallel. According to Wima, the 1000V rating is a bit underrated for pulse applications when I have 475V pulses. So, should I just stay with 47n, or go for 68n - is the value highly critical?
The 56n value FKP1 has been discontinued for a long time.

Instead of the 180nF I currently use, I'll try to source the 1600V R76 series radial capacitor from Kemet (Datasheet: https://content.kemet.com/datasheets/KEM_F3034_R76.pdf) . It comes in a version with long leads, so that would suffice.
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