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Old 2nd Nov 2020, 11:04 pm   #1
unitelex
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Smile Alba 6301 Radiogram restoration plus Bluetooth & DAB

I received the Alba 6301 for repair and restoration, with a request to add Bluetooth/DAB. The Radiogram had belonged to the owner's grandmother and was a cherished item and reminder. Once restored, the plan was to locate it in a new home office, and use it as a sound system for streaming music and audio from modern phone/ipad etc and get a full range of radio programs via DAB, without loosing the original features.

I received the set in June, via courier, the ECC85 had become loose in transit and was rattling around in the base of the cabinet - undamaged!
I removed the amplifier chassis, separate power supply chassis and auto changer deck. The cabinet had some damage so I enlisted the help of Michael (Mancunian69) as I have seen the excellent quality of his cabinet work.

I started with the amplifier chassis, replaced the usual wax capacitors and most some high value resistors, there was evidence that R10 (EBF89 screen) had been overheating most likely due to failed C29. These were replaced.
I would later go on to replacing all resistors on this PCB...
The amplifier uses a pluggable PCB, which is easily removed from the chassis, both PCB and chassis was thoroughly washed and left to dry for a couple of days in a warm spot.
The power supply sub chassis is located in the LH speaker compartment, it is attached via a Octal plug cable. The mains cord feeds the amplifier chassis - to the ON/OFF switch and then the switched mains goes down the octal plug cable to the PSU. Alarmingly the male plug carries the switched AC mains - not a great idea, quite dangerous IMHO. So if you ever work on this set always mate the octal plug if you are applying power !
Octal danger aside, the PSU chassis is quite a useful item by itself it has the mains transformer, EZ81 rectifier, filter resistors and smoothing (3x50uF) Could be useful as the basis of a standalone HT and heater supply for a workshop...
No electrical faults found here, cap reformed OK resistors were OK, EZ81 OK but the chassis was very dirty. After trying various solvents and cleaners with limited success I discovered that the dirt was on top of a wax layer. Boiling water removed it super quick leaving a gleaming zinc plated chassis.
This was then left to dry in a warm spot.

The amplifier and chassis were re-united and gradually powered up through the limiter. All wavebands including VHF came up OK. I proceeded to re-align the IF and this brought useful improvement to the sensitivity.
I was very impressed with the performance at this point, the VHF in particular was very sensitive and distortion free. It has a tuner made by Plessey and this is clearly a good performer. I noted some background hum both at zero volume setting and also with volume at 50%+, interestingly the hum decreased somewhat around the 25% volume setting, some cancellation going on there. I would say these hum levels were no more than you would expect from a set of this vintage (1959), however bearing in mind the owner wanted to operate it as a Bluetooth amplifier, in a quiet office, it is likely the set would be on running in standby with no signal for a long periods so I decided this hum would become an irritation. It had to be improved!
HUM Reduction Investigation...
The amplifier is PCB based. Clearly this saved manufacturing labour , but the single sided copper traces limit the connectivity, they did well to get this tracked with only a single link wire on top of the PCB. But this was done at the expense of some compromise with the heater wiring. The heaters were grounded to the signal ground trace, with a single 6.3V AC heater supply to each valve, resulting in around 3 Amps AC sharing the same ground trace as the signal in places. I suspect they had fun and games trying to implement this while minimizing AC hum into the signal path. The AGC seems to be helping to counter the hum to some extent. Increasing negative feedback (R33/35 increased to 220R each) each made a slight improvement to hum and also signal quality. I tried bridging the grounds with heavy gauge wire, but found that I could improve LH channel at the expense of increased hum on the RH channel and vice versa, or improve hum at low volume settings at the expense of more hum at medium volume setting. I considered re-wiring the heaters with twisted pair and a hum bucking pot with grounded wiper however this would have entailed the same modification within the VHF tuner and I did not want to disturb that.
I did an experiment with a DC feed to the heaters from my regulated bench supply - wow what an improvement! So I set about modifying the PSU chassis to feed 6.3V smoothed DC to the amplifier. A separate Switched-mode power supply, would have been easy but this is a bad idea from the noise perspective. So I decided to stay linear. A regular bridge rectifier was tried but this dropped too many volts leaving around 5V DC. A bridge was made from 4 x 10A schottky diodes, and together with 2 x 15,000 uF, 0.2 OHM 14W series resistor and another 2 x 15,000uF resulted in a very clean 6.3V DC under the expected load. Rectifying the heater supply puts additional load on the transformer (some power dissipated in the 0.2R) so the EZ81 was replaced with 2 x 1N4007 and an additional dropper resistor. Also the dial lamps were changed to LED - see later. Since the EZ81 heater consumes 1A and the dial lamps 2 x 300mA this was a reasonable reduction to compensate for the added load due to rectification. The HT and DC heater supplies were loaded up with dummy loads and ran for many hours with a 250V AC feed from the variac. The transformer and other parts only becoming slightly warm so I concluded it was not overloaded. BTW the schottky diodes had some copper sheet added to each lead near the package to act as heat sinking dissipation to reduce their temperature. They were only running at about 60C but the added copper brought it down to ~50C
The HT was modified with silicon rectifier (2 x 1N4007) as stated, and anti-resonance capacitors added. Although the main 3x50uF reservoir capacitor seemed OK I decided to disconnect it and added 3x47uF 450V high quality caps under the chassis. An additional 47uF was later added up stream of the additional dropper resistor.
I re-tested again with the amplifier connected. Hum was almost gone, but still annoyingly slightly audible even at zero volume setting. It disappeared if the anode of the ECC83 audio driver was grounded. So I added a further RC filter feeding the HT to the two anode resistors (R22, R23 220K each) This consisted of 10K feeding 22uF 450V. This cured the hum completely!
With the ECC83 being fed via the GRAM input from the Bluetooth decoder signal and with zero signal input I could now hear some intermittent rustling from the LH channel only. I tried cleaning the switch contacts, valve bases and PCB surface again but no improvement. The cause turned out to be the 220K anode resistor. I had used NOS 1W carbon resistor, once this was changed for a modern metal film equivalent the rustling disappeared. Both channels were treated to this resistor replacement for good measure.
A final source of noise was radio channel audio bleed through from the long/medium demodulator, either capacitive coupling or PCB tracking etc. This was solved with the addition of a resistor to ground on the amplifier side of C44 where it connects to S12, S13. IIRC I used something like 220K or 470K. This reduced the impedance enough to eliminate this feed through. Since this point is switched out during Gram operation with the crystal cartridge, there is no problem with reduced input impedance into the amplifier affecting low frequency response of the cartridge.
Once these changes had been made the noise floor was incredibly low, both at zero volume setting and even mid to high setting. No hum and barely audible hiss even with the ear right against the speaker. You don't know its on! Puts many modern transistor amps to shame!

Cabinet
The cabinet arrived back, restored beautifully by Michael (Mancunian69). That work is a story in itself due to the difficulty of repairing the formaldehyde varnish type used on this 1959 set, nevertheless the end result was stunning.

New input selection method
An objective of this restoration was to add the Bluetooth/DAB, however I did not want lose any of the original functionality in doing so.
The set has 4 push buttons: LW, MW, FM, Gram. I wanted all these to do exactly as they were intended. All wavebands and the Gram record deck had to work as normal.
But there is now another new input source, namely the Bluetooth/DAB stereo input. How to make that selectable? I did not want to add any external controls either...
Turns out this set has a single unused wafer contact on the LW switch (S21).
S21 works to connect the ferrite rod's LW coil when LW is selected. S21 has its wiper connected to the tuner (L8 transformer) and the normally open contact is wired to the LW coil which is grounded on its far side.
The NC contact was not used.
What I needed was a switched ground signal to drive a relay, the relay contacts (2 pole changeover) would be used to divert the Gram input to the Bluetooth/DAB stereo signal.
So I swapped the allocation of S21 wiper and NO contacts to arrange it so that the unused NC contact would provide a path to ground for the relay via the LW coil whenever LW was not selected.
This then gave me a grounding signal for the relay coil. The relay being energised at all times other than when the LW button is depressed.
The low power relay coil supply (5V 100mW) was taken from the DC heater supply through a dropper resistor. The relay contacts were wired to interrupt the Stereo Gram input between PU (22, 23) and S14, S15. When the relay is in the energised state it connects the Gram cartridge signal to the amplifier and when non-energised it connects Bluetooth/DAB to the amplifier.
So to select Bluetooth DAB the user has to press and latch both GRAM and LW pushbuttons together. I tested it and it worked great! all usual wavebands and Gram also working as originally intended with single buttons depressed as usual.
Bluetooth/DAB
I used the Pure Highway 600 unit, which comes in two parts, 1) small portable battery powered standalone control unit and 2) DAB receiver/antenna cable assembly. The DAB receiver/antennal unit has a stereo AUX cable with 3.5mm stereo plug and a USB type A plug for power feed only.
I added the 3.5mm audio jack socket to the rear of the Alba amplifier, and also a USB panel socket to provide 5V power out of the back of the set. This 5V was generated from the 6.3V heater supply via a LDO regulator mounted to the amplifier chassis. The load for the DAB unit is quite low however it was tested for the full 500mA.
The DAB antenna and receiver was mounted to the rear of the radiogram on the outside using cable ties. It was located behind the RH speaker away from any AC power supplies. The signal was sufficient in this location even when located away from a window. All channels were picked up easily.

As a final enhancement I removed the dial lamps as said earlier. These were giving uneven illumination of the dial, too bright in some places and too dark elsewhere. I replaced these 2 filament lamps with 4 x LEDs and dropper resistors. I used 5mm clear lens types with ~500nm Blue/Green colour. They were arranged in the 4 corners and adjusted to give a very even illumination. I was very pleased with this improvement for two reasons, 1, the colour matches the green shade of the record deck, and 2. the glow is a similar shade of green you get from EM80 and similar magic eyes. It just seems the right colour for this era of set!
Finally the set was fitted with a new 3 core mains lead, earth to chassis and new plug with 3A fuse and PAT tested.
The look and performance is so good I did not want to give it back ! The owner seems very please with it.

https://www.vintage-radio.net/forum/...d.php?t=167809

PS the BSR UA12 auto changer deck needed some work, I might cover that in a separate thread.

Regards
Chris

Last edited by unitelex; 2nd Nov 2020 at 11:13 pm. Reason: improved section heading
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Old 3rd Nov 2020, 12:39 pm   #2
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

What a thorough job! It does sound like the owner's pleased. Jolly well done.

Please show some pictures!
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Old 3rd Nov 2020, 1:04 pm   #3
paulsherwin
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Really excellent writeup Chris, congratulations.
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Old 4th Nov 2020, 9:17 am   #4
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Job well done!
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Old 4th Nov 2020, 2:46 pm   #5
unitelex
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Thanks to all for the feedback.
I am collating some photos to include here
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Old 5th Nov 2020, 7:20 pm   #6
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Thanks Chris, a very interesting write up! Looking forward to photos.
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Old 7th Nov 2020, 1:59 pm   #7
unitelex
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Some photos of the chassis before restoration

1. main stereo amplifier/mono tuner
2. Underside of PCB
3. pair of output transformers
4. Plessey VHF tuner
5. The usual suspects
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Last edited by unitelex; 7th Nov 2020 at 2:01 pm. Reason: added photo descriptions
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Old 7th Nov 2020, 2:05 pm   #8
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Photos (contd.)

1. Amplifier/tuner pcb removed from chassis
2. PCB cleaned, some components changed already
3. PSU chassis before cleaning
4. PSU chassis underside
5. PSU chassis after hot water treatment

BTW I did not allow water into the transformer during cleaning...
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Old 7th Nov 2020, 2:09 pm   #9
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Photos (contd.)

1. Damage to UA12 record deck (damaged in transit)
2. View of damage topside
3. Restored deck
4. New platter rubber
5. Cabinet restored as received from Mancunian69
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Old 7th Nov 2020, 2:11 pm   #10
unitelex
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Here is a picture of the finished item.
Tuning scale with green glow

You can see the portable DAB controller placed on the top of the unit

Best Regards
Chris
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Old 7th Nov 2020, 4:19 pm   #11
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Wow! What an absolutely super job- and a thoroughly enjoyable and informative write-up too.

Steve
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Old 7th Nov 2020, 4:31 pm   #12
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Great job Chris, and a beautiful end result. Its a real bonus when you find an unused switch contact isn't it! There's also some 'spare' in the Quad 2 preamp, allowing the addition of modern connectivity.

Thanks for sharing!
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Old 9th Nov 2020, 12:59 am   #13
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Lovely!

Dave W
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Old 9th Nov 2020, 2:51 pm   #14
Edward Huggins
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The BSR UA12 record deck (Post#9) dates this to late 1958, early/mid 1959. Looks great, one of the last "well built" Albas!
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Old 1st Dec 2020, 11:29 pm   #15
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

That's a really marvellous job. I expect even the cleaning of the circuit board was satisfying judging by the finish you got on those dusty old relics. You can rest well satisfied with this one!

Thank you for the write up - that's the kind of thing that will come in very handy for future visitors.
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Old 4th Dec 2020, 7:23 pm   #16
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Excellent!
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Old 7th Dec 2020, 11:01 pm   #17
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Default Re: Alba 6301 Radiogram restoration plus Bluetooth & DAB

Great write-up and end result! I's nice to see a radiogram saved!
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