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Old 6th Apr 2021, 8:27 pm   #121
DonaldStott
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Default Re: Bush DAC90A - Adding Bluetooth

The resistor I have fitted is indeed 470k - apologies for the typo.

I'll try another temporary lash-up in the next few days and report back. I have checked and double-checked my PCB and circuit diagram and don't see any obvious issues such as a crossed ground pathway or splodges on the BT board?

Fingers crossed that I had a dodgy connection or some other minor annoyance!
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Old 13th Apr 2021, 9:01 pm   #122
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Default Re: Bush DAC90A - Adding Bluetooth

As you would expect my usual stubbornness has made me stick with trying to resolve the DAC90A /Bluetooth issues!

So I tried another lash-up after checking and double-checking the PCB and circuit diagram for any obvious issues such as a crossed ground pathway or splodges on the BT board? Guess what - Bluetooth working as it should with proper loop-through to and from the radio audio. Usual belt and braces made me disconnect everything again to ensure the radio was still working on its own and then back a last time to fitting the Bluetooth PCB and all is still well! I can only assume that I had a dodgy connection or some other minor annoyance!

At the end of the day it now works and the Bluetooth PCB is now fully connected and installed under the chassis of the DAC90A. Just three new holes in the chassis where I've used pan head slotted screws - only a DAC90A 'expert' would spot the change?

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Next challenge is to try and fit the Bluetooth PCB under the chassis of a DAC10 but there isn't much space under there because of the large Tuning Unit used for the push-buttons. What I don't know is to what extent the BT PCB is a 'one size fits all' solution or if the values of the capacitor and resistor need adjusting for other sets. I suppose it's down to our old friend Impedance Matching?

And of course it's a huge thank you to everyone that has persevered through this Thread and especially to those who have made suggestions, tried to help and offered encouragement - it is sincerely appreciated.
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Old 13th Apr 2021, 9:59 pm   #123
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Default Re: Bush DAC90A - Adding Bluetooth

Nice job, well done
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Old 14th Apr 2021, 1:02 pm   #124
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Default Re: Bush DAC90A - Adding Bluetooth

Thanks Gabe.

Does anyone know the operating temperature range for the KRC-86B V4.0 - overheating might be an issue here?
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Old 14th Apr 2021, 1:13 pm   #125
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Default Re: Bush DAC90A - Adding Bluetooth

Quote:
Originally Posted by DonaldStott View Post
Does anyone know the operating temperature range for the KRC-86B V4.0 - overheating might be an issue here?
I wouldn't be worried about the PCB, being installed below the chassis in free air. If you'd somehow fitted it very close to the output valve and dropper resistor that might be different.

The temperature where it is will probably only be 5 to 10 degrees warmer than ambient, I would guess.

Well done on the conversion by the way, it looks very professionally done.

Cheers,
Colin
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Old 14th Apr 2021, 1:52 pm   #126
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Default Re: Bush DAC90A - Adding Bluetooth

Well done!

I would expect module to be good to normal commercial range, eg 70degC
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Old 14th Apr 2021, 3:20 pm   #127
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Default Re: Bush DAC90A - Adding Bluetooth

I'm sure you'll be ok regarding temperature. Does the metal chassis reduce the BT range a bit?
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Old 14th Apr 2021, 3:26 pm   #128
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Default Re: Bush DAC90A - Adding Bluetooth

Quote:
only a DAC90A 'expert' would spot the change?
Metric screws! Joking apart, a very neat workman like job.

Edit, of course BA is a metric thread I should have said ISO metric.
 
Old 14th Apr 2021, 5:50 pm   #129
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Default Re: Bush DAC90A - Adding Bluetooth

Hi Donald, nice work! Well done so glad your perseverance has payed off.
Just wondered if you had seen the recent threads regarding the minimod pantry transmitter pcbs that Electronpusher has made and kindly offered to forum members.
I have made one and have been so impressed with the audio quality and ease of setup. It really feels good to actually tune in a medium wave signal you are transmitting even if it is only for a few feet. I think in future I will use these in preference to the bluetooth route especially with live chassis and compact sets.

Kind regards RT
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Old 15th Apr 2021, 12:29 pm   #130
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Default Re: Bush DAC90A - Adding Bluetooth

As with every new build there is always a period of snagging ...!

Over the last few days I've been happily listening to numerous radio stations and podcasts using my DAC90A with added Bluetooth functionality. I am now, however, experiencing intermittent lost connections? The Bluetooth audio stops and we hear the usual background hash but I can retune the radio to a station e.g. BBC Radio 4 LW. When I turn off Bluetooth on my iPhone and turn it back on again (the usual IT Technicians' fix all solution) I am unable to connect to the KRC-86B? I have to turn the radio off and back on again to reconnect? Sometimes there are no lost connections for 20-30 minutes while at other times it's only 2-3 minutes!

At first I was concerned that I may have an overheating issue but I moved the DAC90A to a cooler part of the room and have been running it with the back cover off - no improvement?

I know that this isn't a Forum for discussing Bluetooth problems but just thought I'd put it out there as this is such a niche installation. I understand that there are 1,001 possible causes of Bluetooth lost connections but I'm struggling to discern a pattern here?

Anything in particular that springs to mind with this particular KRC-86B Bluetooth module that could be causing these problems?
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Old 15th Apr 2021, 2:04 pm   #131
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Default Re: Bush DAC90A - Adding Bluetooth

Two things come to mind

Either the metal chassis blocking the BT signal and severely compromising your range or the device is pairing with something else. Whist it is paired with something else you'd be unable to connect with your phone.

It may be a combination of the two - you go out of range and connection drops, module pairs to other phone/laptop etc leaving you unable to connect until you turn it off and on again

Last edited by Gabe001; 15th Apr 2021 at 2:21 pm.
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Old 15th Apr 2021, 3:19 pm   #132
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Default Re: Bush DAC90A - Adding Bluetooth

Thanks for the suggestions Gabe - I've gone round the entire house and ensured that Bluetooth is turned OFF on every device we have!

If there was an issue with the metal chassis blocking the BT signal then I would have thought I couldn't pair at all? I've taken my phone two rooms away and it still pairs with the KRC-86B?

My phone is now sitting adjacent to the radio and I've just had another lost connection! After switching the radio off and on a few times I was unable to connect to the KRC-86B for about 10 minutes.

Of course I'm trying to avoid the inevitable which involves removing the chassis again to see if there any obvious problems! I'm fairly new to Bluetooth (!) so it's a steep learning curve.
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Old 15th Apr 2021, 3:34 pm   #133
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Default Re: Bush DAC90A - Adding Bluetooth

I think you're going to have to hook a voltmeter on the 5v and make sure it's not collapsing.

FWIW my KRCs do not show any tendancy to drop out.
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Old 15th Apr 2021, 3:45 pm   #134
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Default Re: Bush DAC90A - Adding Bluetooth

My krc-86b doesn't drop out either. I think you need to do as Paul says. If you're using one, the 7805 can go into thermal shutdown if it gets hot.

Last edited by Gabe001; 15th Apr 2021 at 3:51 pm.
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Old 15th Apr 2021, 3:57 pm   #135
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Default Re: Bush DAC90A - Adding Bluetooth

I think you might find the problem is a slight voltage dip, I had trouble with dropping out when I fitted krc module into a bush srp 31c, spent some time working on the power supply to get it right. Also using the same regulator.
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Old 15th Apr 2021, 8:56 pm   #136
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Default Re: Bush DAC90A - Adding Bluetooth

Voltage drop - interesting line of enquiry!

Just for the record I'm using the 78L05 regulator and in accordance with the datasheet a 330 nF on the input and a 10 nF on the output.

Watching my DMM on the 5V line from the 78L05 is my first job for tomorrow, Friday.

What are the critical voltages for the KRC-86B, especially minimum?
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Old 15th Apr 2021, 11:41 pm   #137
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Default Re: Bush DAC90A - Adding Bluetooth

In my experiments anything below about 3v3.

In practice because the current demand is quite spiky if you start to see a voltage measurement below say 4.75v from your regulator it could well be that troughs are below 3v3.

In my Blaupunkt I use a 7805 (not L) and have not had any trouble. Do you have the supplied 470uf cap soldered to the module supply pins?
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Old 16th Apr 2021, 10:49 am   #138
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Default Re: Bush DAC90A - Adding Bluetooth

Thanks Paul for your continuing interest and support.

Intriguing readings this morning...

Connected up my DMM to the GND and OUT pins of the 78L05 as this was the most convenient place. Turned on the radio and the voltage rose to around 4.87V and was quite steady. Turned on Bluetooth on my iPhone and paired with the KRC-86B and the voltage dropped to around 4.5V. Turned on BBC Sounds on the iPhone and played Radio 4 - voltage dropped to around 4.15V but was very spiky indeed. Over a period of about 10-15 minutes I watched the spiky voltage gradually drop to around 3.3-3.7V and then I lost the connection! Turned off everything and back on again and then tried to pair with the KRC-86B but kept on getting "Connection Unsuccessful" - voltage reading was showing 4.35V?

So the obvious implication of the above is that I may have a voltage regulation problem, possibly with the 78L05? This can easily be replaced by a 7805 but according to the datasheet a 330 nF is recommended on the input and a 100 nF on the output.

My PCB circuit is as shown in Post #72 above from David G4EBT.

https://www.vintage-radio.net/forum/...7&postcount=72

The 470uF electrolytic capacitor supplied with the KRC-86B has not been soldered to the module supply pins.
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Old 16th Apr 2021, 11:27 am   #139
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Default Re: Bush DAC90A - Adding Bluetooth

The 470uf electrolytic will help smoothen the spikes. If you do fit it in though, it's good practice to place a diode "in reverse" across the regulator so that the capacitor doesn't discharge into the regulator. See my power supply circuit attached.

My money is on the regulator overheating due to the high ambient temperature and the fact you're driving it quite hard with probably around 10.5v going in. Try lowering the input voltage using a couple of diodes in series to give you a 2.2v drop and see if the problem goes away.
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Old 16th Apr 2021, 11:31 am   #140
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Default Re: Bush DAC90A - Adding Bluetooth

Quote:
Originally Posted by DonaldStott View Post
So the obvious implication of the above is that I may have a voltage regulation problem, possibly with the 78L05? This can easily be replaced by a 7805 but according to the datasheet a 330 nF is recommended on the input and a 100 nF on the output.

My PCB circuit is as shown in Post #72 above from David G4EBT.

https://www.vintage-radio.net/forum/...7&postcount=72

The 470uF electrolytic capacitor supplied with the KRC-86B has not been soldered to the module supply pins.
The spec says the KRC-86B will operate from 3 - 5V, but no mention of the current drawn.
That said, I wouldn't have thought that the current drawn would be in excess of the upper limit of 100mA that the 78L05 can handle, but it doesn't seem very happy. (The rated output of the 9V transformer used is 133mA).

https://roboeq.ir/files/id/3237/name/KRC-86B%20V4.pdf/

I guess you could try a 7805 (1 AMP) regulator, at least as a temporary substitute for the 78L05, but bear in mind that the pinouts differ. (See diagrams attached).

I wouldn't have thought that the location of the PCB on the rear apron of the chassis would be problematical. It isn't near any heat generating components and there's really nowhere else it could be sited. A rather irksome setback after what seemed to be a very successful outcome, but I know you'll get it sorted as you are aligned with the 'Churchillian mindset' that 'success is the result of going from one failure to another with no loss of enthusiasm'!

So, the Ekco U122 is on the back burner for now, and will have to wait its turn.

Good luck with it.
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