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Old 11th Oct 2020, 7:27 am   #21
crackle
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Default Re: More BUSH DAC10 Woes!

I cant see any connection to the scale dial bulbs. I assume you will connect one end of the dropper resistor on bulb one to ground and the other end of the dropper resistor on bulb 2 to the mains switch.
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Old 11th Oct 2020, 9:30 am   #22
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by crackle View Post
I cant see any connection to the scale dial bulbs. I assume you will connect one end of the dropper resistor on bulb one to ground and the other end of the dropper resistor on bulb 2 to the mains switch.
Mike
Well spotted Mike.

Work in progress - didn't want to make those final connections just in case someone spotted a 'show stopper' with what I've done already?
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Old 11th Oct 2020, 11:41 am   #23
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Default Re: More BUSH DAC10 Woes!

Just a quick follow up - you can spot the wires that will be connected in the bottom right of my second picture in Post #19 above. I just moved them out the way to ensure a clearer view.

Red and Yellow for the dual can electrolytic and Blue and Brown for the scale dial bulbs.
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Old 18th Oct 2020, 11:10 am   #24
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Default Re: More BUSH DAC10 Woes!

There have been a couple of diversions to this Thread while I sorted out issues with the Bush DAC10 - MW Frame Aerial and Restuffing Dual Electrolytic Can Capacitor. These are now resolved, hopefully, and we can get back on track with this set?

I did experience another slight delay as I'd forgotten about the wiring and soldering associated with the Output Transformer and Loudspeaker which all had to be replaced - some more solder joints for you to peruse: -

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The Tone correction capacitor (C24) that was fitted across the Primary of the Output Transformer was 0.022uF whereas the Bush Service Instructions lists this as 0.1uF, so this was changed accordingly. The replacement was a 1kV capacitor, just in case!

So for the first time we were able to re-assemble all the component parts of this set preparing for an initial live switch on, with the lamp limiter of course! Flick the switch and watch the bulb in the lamp limiter initially dim and then slowly brighten as the radio came alive!

First thing I noticed was no hum which I can only put down to the new reservoir and smoothing caps, proving that my re-stuffing exercise had been successful? Reception on MW was surprisingly good which amazed me as this was using my new Frame Aerial winding although LW was quite poor with only a couple of stations with lots of background noise! The on-off switch/volume control did not have any scratchiness which was more good news. Switched from Lamp to Direct after about half an hour and everything sounded a bit better but still not great on LW.

Still work to be done...

Time to take some voltage readings for the various valve pins - input mains voltage was 240V AC at the time with the receiver set to MW range with no signal. Values stated are as specified in the Bush Service Instructions while those in brackets are what was measured: -

V1 UCH42
Pin 2 98 (76.8)
Pin 3 47 (39.9)
Pin 5 47 (40.2)
Pin 7 N/A (0.84)

V2 UF41
Pin 2 74 (58)
Pin 5 57 (46)
Pins 3,4 & 7 0.8 (0.96)

V3 UBC41
Pin 2 74 (45.2)
Pin 7 1.3 (0.96)

V4 UL41
Pin 2 190 (178)
Pin 5 98 (77.1)
Pins 3 & 7 5 (3.9)

V5 UY41
Pin 2 220 A.C. (194 A.C.)
Pin 7 205 (189)

The HT seems low all across this set but I'm sure there is a lot more going on - any advice or guidance would be welcomed??

I'm going to check again and remind myself which LW and MW stations should be available for my local transmitter and see how these correlate with the stated wave ranges.

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I know that FM and Freeview come from Black Hill but wasn't aware that MW and LW transmissions came from Westerglen and Dechmont Hill - see this page: -

Radio stations in Glasgow

As I've installed a new MW winding on the Frame Aerial I've assumed that some from of re-alignment will need to be carried out with this set. With the tuning capacitor vanes fully meshed the Cursor isn't too far off the datum line on the auxiliary calibration scale: -

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Old 18th Oct 2020, 7:55 pm   #25
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Default Re: More BUSH DAC10 Woes!

Hi Donald, a good effort, you may find that in Glasgow there is not much in the Way of LW reception. There are French ans Irish stations, but they may be screened where you are.


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Old 19th Oct 2020, 1:02 pm   #26
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by Ed_Dinning View Post
Hi Donald, a good effort, you may find that in Glasgow there is not much in the Way of LW reception. There are French ans Irish stations, but they may be screened where you are.
Thanks Ed - I'm still amazed that my new MW Frame Aerial winding actually works! It's my first attempt at this so quite pleased.

The MW reception on this set is now good although up here we do suffer from a dearth of stations to listen to. I have very good reception for the following:-

Absolute Radio (1215kHz, 246metres)
Clyde 2 (1152kHz, 260metres)
talkSport (1089kHz, 275metres)
BBC Radio 5 Live (909kHz, 329metres)
BBC Radio Scotland (810kHz, 370metres)

Although the Bush DAC10 MW range extends from 190-565metres I only have a very faint BBC Radio Ulster at 223metres (1341kHz) and nothing whatsoever between 370-565metres - almost half the dial!

We only seem to have two LW stations available:-

BBC Radio 4 (198kHz, 1514metres)
RTÉ Radio 1 (252kHz, 1189metres) - very faint!

The LW range is very noisy with lots of background hash but this isn't an issue with any other radios in the same room e.g. Bush DAC90A.

So still looking for any advice or guidance on how to improve LW reception on this set?

What is interesting (?) is that Radio 4 LW is louder when tuned in via one of the Pre-Set switches as opposed to manual tuning on the LW Pre-Set switch. It is louder but so is the background noise so maybe a couple of problems there??

I've swapped the rectifier valve (UY41) and the output valve (UL41) for known working valves but these made no difference to the HT unless all these valves suffer from low emission?

Where to next ...?
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Old 19th Oct 2020, 2:18 pm   #27
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Default Re: More BUSH DAC10 Woes!

Just to note, on LW the LW aerial coil is connected in series with the MW aerial coil, also the setting of the MW aerial trimmer will affect the LW aerial tuning capacitance especially at the higher end of the LW band.

Lawrence.
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Old 19th Oct 2020, 8:00 pm   #28
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by ms660 View Post
Just to note, on LW the LW aerial coil is connected in series with the MW aerial coil, also the setting of the MW aerial trimmer will affect the LW aerial tuning capacitance especially at the higher end of the LW band.
Thanks Lawrence - duly noted.

The LW range on the Bush DAC10 is 845-2070 metres (355-145kHz) and Radio 4 is at 1514 metres (198kHz) - so roughly in the middle of the range and not at the higher end.
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Old 19th Oct 2020, 8:06 pm   #29
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Default Re: More BUSH DAC10 Woes!

And the two coils are definitely aiding?

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Old 19th Oct 2020, 8:26 pm   #30
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by Ed_Dinning View Post
Hi Donald, a good effort, you may find that in Glasgow there is not much in the Way of LW reception. There are French ans Irish stations, but they may be screened where you are.


Ed
Hi Ed

Radio 4 on Long wave should be good in Glasgow as Westerglen has simultaneous transmission on 198khz. RTE 1 on 252khz should be receivable too but weaker.
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Old 19th Oct 2020, 8:48 pm   #31
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by ms660 View Post
And the two coils are definitely aiding?

Lawrence.

That means the coils should be in phase...wound in the same direction and mounted so that the windings are connected in phase. If one of them is connected out of phase, they will be subtracting from each other rather than adding.
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Old 19th Oct 2020, 8:55 pm   #32
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by Sideband View Post
Quote:
Originally Posted by ms660 View Post
And the two coils are definitely aiding?

Lawrence.

That means the coils should be in phase...wound in the same direction and mounted so that the windings are connected in phase. If one of them is connected out of phase, they will be subtracting from each other rather than adding.
Or in simpler terms both wound in the same direction with the finish of one coil connected to the start of the other coil, get that wrong and the overall inductance will be reduced.....:

https://www.electronics-tutorials.ws...inductors.html

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Old 19th Oct 2020, 9:35 pm   #33
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Default Re: More BUSH DAC10 Woes!

The new MW coil was wound following the advice from Forum member Shuttle in Post #10 here:- Bush DAC10 - MW Frame Aerial - thanks again Arthur!
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Old 19th Oct 2020, 9:48 pm   #34
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Default Re: More BUSH DAC10 Woes!

Did the RF circuits need any alignment adjustments?

Lawrence.
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Old 20th Oct 2020, 9:42 am   #35
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Default Re: More BUSH DAC10 Woes!

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Originally Posted by ms660 View Post
Did the RF circuits need any alignment adjustments?
I haven't touched the RF alignment as I was focusing on trying to improve the HT in the first instance? Very low on V2 and V3 for example - see Post #24 above?

I need to acquire a set of alignment tools and fabricate a " ... single turn loop of wire approximately 10 by 8 ins" as per the Service Instructions. Although I now have a working sig gen, frequency counter and 'scope I have no intention of being the 'Phantom Twiddler' especially on a working set!
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Old 20th Oct 2020, 10:22 am   #36
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by DonaldStott View Post
Although I now have a working sig gen, frequency counter and 'scope I have no intention of being the 'Phantom Twiddler' especially on a working set!
It's always good practice to check the alignment of tuned circuits that have had a component replaced.

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Old 20th Oct 2020, 12:14 pm   #37
DonaldStott
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Default Re: More BUSH DAC10 Woes!

I'm going to refashion these tools which I've used previously to open iPads and iPhones:-

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Meantime does anyone have some guidance on what the " ... single turn loop of wire approximately 10 by 8 ins" as per the Service Instructions looks like?

And what about the HT, especially V2 and V3?
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Old 21st Oct 2020, 11:03 am   #38
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Default Re: More BUSH DAC10 Woes!

Quote:
Originally Posted by ms660 View Post
Did the RF circuits need any alignment adjustments.
I tried a bit of 'twiddling' with the RF but couldn't hear any appreachiable difference?

Still a lack of sensitivity and lots of background noise on LW !!!
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Old 21st Oct 2020, 2:36 pm   #39
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Default Re: More BUSH DAC10 Woes!

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...does anyone have some guidance on what the " ... single turn loop of wire approximately 10 by 8 ins" as per the Service Instructions looks like?
Just as the datasheet says - a loop of wire which is place close to the frame aerial, (within 30cms or so) with the signal generator output could to each end of the wire, with the signal generator tuned as outlined in the datasheet (at the points on the dial stated in the data) to give maximum output on MW (L4/L6/TC1), then on LW, (L6/L7/TC7).

The IF stages should be checked/aligned first, for which the loop isn't needed as the generator is first connected to the control grid (pin 6) of V2 to align IFT2 primary and secondary, then IFT1 primary and secondary in that order.

If you don't feel confident to realign the set if need be, you won't do any harm by at least doing some basic checks by for example, sweeping the generator either side of the expected frequencies to see if the tuning seems reasonably accurate, as it might well be. But that said, you do have a counter and signal generator, unlike the 'phantom twiddlers' who only have a screwdriver. Really, unless you attempt to realign the set in accordance with the Bush step by step instructions, you're never going to know whether it's working at its best.

Because I'm a bit that way inclined, I made a 20cms wooden support for a single turn loop of insulated wire for alignment purposes, and the rather nifty little audio output meter which Paul Stenning design many years ago, in the hope and expectation that when I can get back to it, I'll eventually get my recalcitrant DAC90A working. So - I have a working loop, and audio output meter, and a non-working DAC90A = 'A' for effort, 'D' for attainment!.

Just to reiterate that you must not of course connect mains powered test equipment to a live chassis set unless the set is powered from a main isolating transformer, which I'm sure you know.

Hope that helps a bit.
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Old 21st Oct 2020, 5:15 pm   #40
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Default Re: More BUSH DAC10 Woes!

Thanks David for yet another informative Post but as usual you've set the bar high with your " ... 20cms wooden support for a single turn loop of insulated wire for alignment purposes" - very impressive! I'll probably knock something together with a bit of MDF and some PVA.

I've never tackled alignment before, as you know, as I'm very wary having read too many horror stories about this procedure going very wrong! Adjusting the Pre-set switches in this DAC10 was fairly straightforward and I had a bit of a 'twiddle' with the RF but not much improvement there - just using my ears of course! What I've also done is to sweep the signal generator either side of the expected intermediate frequency of 465kHz and a definite signal from the radio is heard rising and falling with just a wire draped across it.

IF alignment seems slightly scary but I'm saved from that for the moment as I don't have an isolating transformer - that was close! I also don't have the Paul Stenning audio output meter or similar so the DAC10 can go on hold until these two items of workshop equipment are acquired.

I'm still concerned about the Frame Aerial as I had to rewind the MW wiring so I'm thinking that the LW winding could be suspect as well? After some adjustment the MW winding inductance was reduced to 0.17mH but I note that my reading across the LW winding is 1.69mH - that's connecting Tags A and B where shown in the third picture of Shuttle's earlier Post here - https://www.vintage-radio.net/forum/...3&postcount=10 - is this problematic?

Can anyone help with a measurement of the inductance for the LW winding on the Bush DAC10 Frame Aerial - thanks in advance.
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