Bush DAC90A FM Conversion
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Hi ordered the David Winter FM board for tube radios & while I am waiting for for it to arrive I am preparing this DAC90A chassis for my ivory set . 1st thing I have done is give it blanket change and stuff the waxie capacitors replace with a NOS volume pot / switch & as recommended class x2 10nf suppression capacitor across the switch .Old wiring has been changed next step is to change the mains dropper to the Ed Dinning auto transformer hear is some pictures more to follow
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Re: Bush DAC90A FM Conversion
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Hi Bob,
in order that a three position waveband switch can be fitted in a DAC90A, modifications to the switch bracket are called for. A very small four-pole three-way switch measuring only 28mm diameter can be fitted in the extra space made for it. See attachments. DFWB. |
Re: Bush DAC90A FM Conversion
Hi Bob, looking forward to hearing how you get on with this project, I have also ordered a module to try not sure what I am going to use as a test bed yet.
Kind regards RT |
Re: Bush DAC90A FM Conversion
I am also looking forward to hearing how you get on, having ordered some of David's modules.
I have previously converted a few DAC90A sets - some to FM and one to DAB, using the also excellent modules from HSE. Plenty of owners have DAC90 sets, and love the idea of being able to listen to their everyday stations on them! |
Re: Bush DAC90A FM Conversion
Hi David adaptor plates here we go . Hi RT the audio amp stage on this DAC90A there is no noise so the sound quality on FM is going to be very good will report findings as it happens
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Re: Bush DAC90A FM Conversion
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Re: Bush DAC90A FM Conversion
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I really like the look of David's modules, but think there is also a place for the HSE ones. Easier to integrate the HSE module particularly in a live chassis and series heater chain, as you don't need to consider power. That said, they have to be built for the particular set and obviously cost a lot more. Each set/customer is different, so it is great to have both solutions available. I think the demand for FM and indeed DAB conversions will only increase with time. |
Re: Bush DAC90A FM Conversion
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Re: Bush DAC90A FM Conversion
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Here's a rare frontal view of the DAC90A :-] Attachment 244424 How about mounting an extra 500pF VC for exclusive use of the module, to a shaft coupler stuck (somehow) to the shaft? But to be honest I think there is a different simpler approach that needs to be considered. Why not couple a potentiometer to the tuning gang and use an FM receiver with varactor / varicap diode tuning of the sort that were common 30 or 40 years ago. What does the team think? |
Re: Bush DAC90A FM Conversion
I was thinking along the same lines but using a single 500pf tuning capacitor, driven from the dial cord , I guess only certain sets would would be viable, Mick.
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Re: Bush DAC90A FM Conversion
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NEWS-FLASH looks what has arrived from France ( Very quick postage ) thanks David :thumbsup: Waiting for a anti static wrist band to arrive from the UK that is taking longer before I start to work on it
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Re: Bush DAC90A FM Conversion
Awesome.
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Re: Bush DAC90A FM Conversion
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Re: Bush DAC90A FM Conversion
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UPDATE could not wait for the anti static strap to arrive bought a anti static mat and followed Davids instructions temporary wired the board on the antistatic calibrated it and a great result board works fine. Two points to consider 1. as David says the tuning gang has to be perfect and the other is the radio being a DAC90A ( not the board ) needs some work on the audio stages. I am very pleased with this board and how easy it is to set up. I'm going to order another board as this is going to be FM only. Here are some pictures, more to follow when the board is installed.
Kind regards, Bob :thumbsup: |
Re: Bush DAC90A FM Conversion
Hi Bob well done :) Great to hear that the board worked straight away, I thought it would be hard to resist wiring it up. I am thinking of fitting this module to my Philips 462A it has a large speaker and great sound when fed from the gram input or a Minimod.
I will follow your progress and will post some pictures when my module is wired up and tested Kind regards RT |
Re: Bush DAC90A FM Conversion
Hi RT as David Winter says in his instructions the board should be well grounded and the tuning capacitor must have no faults one thing I am going to do is install the board close to the tuning capacitor so there is no long wire run . it will sound really great in your Phillips 462A
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Re: Bush DAC90A FM Conversion
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With modification to the bracket the 4 pole 3 way Lorlin switch will fit in the space between the control shaft and the and the wavechange switch.
But more clearance is needed to avoid the tags on the new switch coming into contact with the tuning control shaft. DFWB. |
Re: Bush DAC90A FM Conversion
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I've done a number of radios with a "long" wire between the tuning capacitor and the board (maximum 10 inches). Never a problem, but I awlays place the board as close as I can from the tuning capacitor. If the wire has to be that long, I make sure it is hard enough to stay free. And even if you have to make the wire pass here or there, the added capacitance won't hurt as the calibration steps will take this into account automatically. However, use a shielded audio wire (I personally ground it using the electrolytic capacitor's negative pad, which makes it easier to connect only one hot point to the amplifier's input. The only cases where I used a single, non shielded wire was when the board was close enough to the amplifier's input or from a shielded wire going to it (i.e maximum 2 inches). I once had too much residual hum on a radio and used a 3-wire mains cord with chassis to the earch, thus removing those capacitors between the mains and chassis (and adding one over the mains switch). As a result, the radio was absolutely NO residual hum. However, I think I once had another case of "earthed chassis" where I had no hum only if the phase arrived to one specific edge of the mains transformer. By the way, it would be interesting for everybody following this thread that you add a video of your radio working. |
Re: Bush DAC90A FM Conversion
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The bracket has been repositioned again to make more space for the switch tags.
DFWB. |
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