Author Topic: Quad 303 restoration  (Read 2486 times)

Offline marantz123

  • Trade Count: (+1)
  • AVForums Veteran
  • ***
  • Posts: 338
  • Total likes: 17
  • I learnt more from The Internet when it was slower
Re: Quad 303 restoration
« Reply #120 on: January 11, 2019, 09:15:15 PM »
Man...this is a lovely thread!! Its been ages since we had such detailed diy and so many pics step by step....thank you!!! One question, what varnish did you use?

Offline mygoggie

Re: Quad 303 restoration
« Reply #121 on: January 12, 2019, 07:35:43 AM »
Man...this is a lovely thread!! Its been ages since we had such detailed diy and so many pics step by step....thank you!!! One question, what varnish did you use?

Thank you @marantz123, I am a firm believer in learning and sharing so others can learn as well.

The varnish ... I gave this a lot of thought and some more. And then went with what I had in my workshop. Good old Woodoc 10 for the simple reason I know it penetrates everywhere and it dissolves oil and dirt on it's own so it should reach and clean the spots I could not get too and at the same time do its coating job. In addition it is a polyurethane and wax combination which renders a very flexible sealing coating. I have used this varnish in the weirdest of applications over the last 40 years and it always just works.

The idea is to put the transformer caps on once I had these cleaned and then dunked the whole assembly two more times.

First on to testing the transformer under load today.
Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #122 on: January 12, 2019, 10:18:38 AM »
So today's quest is to build a load that can vary and at the same time run on 63VAC. I looked a bit on the internet and could not find anything that is not expensive or fun to use.

Time to make my own design and see if it works. I had a bunch of automotive bulbs and some wires and connectors in my treasure trove and this looked like a fine option. Just some ramblings from hereon for myself and to see if my mathematics still makes sense.

So a 12V automotive bulb will work on AC or DC, so that should not be an issue. Five bulbs in series at 12V each will give me 60V. A little under 63V, but I think the bulbs can share the 3V between themselves and not get damaged.

Each bulb is 21W, so 21W x 5 = 105W which is just over half of what the transformer rating of 200VA is. This is good as I can start up at 50% load and increase the load by adding bulbs in parallel when I think it is safe to do so.

Let's determine what the actual power rating in Watts will be in terms of bulbs to get close to the 200VA. Now an incandescent bulb has a power factor of very close to one, so lets be on the safe side and use 0.98. Our 200VA full load, will therefore be reached if I use 200VA * 0.98 = 196W of bulb load. So let's try nine bulbs. The demand of these bulbs will be 9 x 21W = 189W which is 196W - 189W = 7W less than max capacity. Great!

Onto building something fun.

The electrical stuff I want to use, and yes the bulbs were corroded and I had to clean them ...






I had some scrap wood and quickly planed a short piece of meranti into shape and drilled nine spaces for bulbs and some holes for wires.

The basic idea made into an object and ready to be varnished. I wonder why I have varnish available?  :thinking:





Going the way of the transformer ...





While the plank is drying, I think I need to rest a bit and listen to some good blues.  :groovy:

Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #123 on: January 12, 2019, 12:07:17 PM »
Good thing I listened to the Blues ... I realised I forgot to allow space for the wiring on the underside of the board.

I took out the Stanley 78 and five minutes later, there was space!




Gave the board a second coat of varnish and while it is drying I made the banana socket holder plate.

I found a scrap piece of aluminium from my plate treasure trove and marked out what is to be what. All holes marked and drilled.





And the plate ready to be screwed to the board. Just waiting for the varnish to completely dry.

« Last Edit: January 12, 2019, 07:02:59 PM by Family_Dog »
Herman

~ To heal the soul is to embark on a new journey. ~

Offline HB

Re: Quad 303 restoration
« Reply #124 on: January 12, 2019, 04:05:27 PM »
No pics! :nfi:
When You Come to a Fork in the Road, Take It!            [Yogi Berra]

Offline mygoggie

Re: Quad 303 restoration
« Reply #125 on: January 12, 2019, 04:42:55 PM »
No pics! :nfi:

This is silly, sometimes the images work and sometimes they do not. Sorry will ask @Family_Dog to sort out._
« Last Edit: January 12, 2019, 05:04:19 PM by mygoggie »
Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #126 on: January 12, 2019, 04:47:22 PM »
Let me complete the load board construction here.

The next step was to solder leads onto the light bulbs. I use my favourite holdfast which is a corduroy bag filled with dried used coffee grinds. Here is the first bulb in place.





I think very few people know that phosphoric acid is an excellent flux for soldering. So here I run a small bead of acid down the side of the bulb.




A very quick touch with some solder and it is tinned.





And the lead is easily soldered onto the casing.





I am not a fan of hot glue, but today I decided to use some to keep the wires in place. All wired up and as neat as I want to go today.




Topside looks good.





Glowing well at 30V. Yes I ran out of banana plug. Using the Africa way ....






« Last Edit: January 12, 2019, 05:03:20 PM by mygoggie »
Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #127 on: January 12, 2019, 05:04:33 PM »
I made a design mistake and I am trying to figure out a solution. I forgot that when cold a bulb filament has almost no resistance. So what happens is that the transformer is almost shorted out on secondary when the cold bulbs are connected and the 220VAC load protection (current limiting) lightbulb burns a bright white. When I add in a 10k resistor the current limiting bulb stays unlit, but the transformer starts to hum, meaning it is in overload.

So if you have some idea what to do let me know. I know there are a solution where you add an electronic circuit but what is in that circuit is a mystery.
Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #128 on: January 12, 2019, 05:46:50 PM »
After searching a bit I found this thread which looks like what I need.

Now to figure out what I need to do ... I am still open for ideas!
Herman

~ To heal the soul is to embark on a new journey. ~

Offline Family_Dog

  • Administrator
  • Trade Count: (+26)
  • *****
  • Posts: 8,701
  • Total likes: 77
  • STEEL & GLASS - Everlasting Beauty!
    • Repcom 2-way Radios
Re: Quad 303 restoration
« Reply #129 on: January 12, 2019, 06:16:41 PM »
Herman, the second pic link you sent me does not work, I replaced it once again with the original link, and it shows for me. But then, so did the original three pics as well.

Something does not gel: When the Quad starts up with a normal Bridge (?) rectifier and smoothing cap, there is also a sudden inrush of current - momentarily - while the cap charges. So the cold starting resistance may be equated to that as well, it should only be a moment or so and then the five globes should be glowing brightly.

Adding a current limiting resistor would work - but 10k? I would go no higher 10-15 ohms, but it would have to be a suitable rated wire-wound resistor of around 20w minimum, it would only need to be in circuit for a second or two and then you can short it out completely. (My figures here are not calculated, but thumb-sucking).

The load you are using (sans current limiting resistor) is 105 watts, what is the wattage of the series globe in your AC protection circuit? If 60w or less, then therein lies the problem. If you do not have a 100w globe, substitute with a fuse, 2 - 3 amps in the AC side.


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline mygoggie

Re: Quad 303 restoration
« Reply #130 on: January 12, 2019, 06:56:02 PM »

Adding a current limiting resistor would work - but 10k? I would go no higher 10-15 ohms, but it would have to be a suitable rated wire-wound resistor of around 20w minimum, it would only need to be in circuit for a second or two and then you can short it out completely. (My figures here are not calculated, but thumb-sucking).
 

I know, that was the only wire-wound one I had and it was just to check if a resistor will make a difference.


The load you are using (sans current limiting resistor) is 105 watts, what is the wattage of the series globe in your AC protection circuit? If 60w or less, then therein lies the problem. If you do not have a 100w globe, substitute with a fuse, 2 - 3 amps in the AC side.

 :facepalm: you are correct. I forgot to replace the 60W bulb. Will check now.
Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Re: Quad 303 restoration
« Reply #131 on: January 12, 2019, 07:26:47 PM »
Transformer inductance played me a curved ball today! Thanks Eric for assisting.  :dop: :dop:

As we learned when I was young: "If all fails, you have overlooked the obvious". Certainly the case here!

I added another 60W in parallel to the existing one in the primary 220VAC feed and she started up! As the output of the isolation transformer is fully protected with a 2A circuit breaker, I then removed the two light bulbs and presto ...

Herman

~ To heal the soul is to embark on a new journey. ~

Offline mygoggie

Quad 303 restoration - Transformer
« Reply #132 on: January 12, 2019, 08:08:30 PM »
I left the transformer running with a 105W load for one hour and listened to some more Blues ...

A quick check on the transformer after an hour showed the secondary voltage has dropped a slight bit. I then tried to determine the temperature of the transformer, but it was so ever slightly more warm than ambient I had to make sure again. Yes, it is a little warm to the touch, but nowhere near the temperatures I read other people experienced.

As I switched the transformer off, the first bulb in line blew. I read somewhere this can be the case. Not going to worry about this.

Maybe I will add in the extra four bulbs tomorrow or maybe I will call it a good test and go on with other things.

After one hour she is running sweetly.

« Last Edit: January 13, 2019, 01:36:33 PM by Family_Dog »
Herman

~ To heal the soul is to embark on a new journey. ~

Offline Family_Dog

  • Administrator
  • Trade Count: (+26)
  • *****
  • Posts: 8,701
  • Total likes: 77
  • STEEL & GLASS - Everlasting Beauty!
    • Repcom 2-way Radios
Re: Quad 303 restoration
« Reply #133 on: January 12, 2019, 09:31:24 PM »
Good show, Herman. The lower voltage could be as a result of a lower grid voltage, up here everyone is running air-cons in scorching temperatures. I would think your transformer is completely good to go.
 

Pity the pic above is not working though...   :teach:

Send me a new pic-link and I will insert it.


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline mygoggie

Re: Quad 303 restoration
« Reply #134 on: January 15, 2019, 02:09:42 PM »
I have not been feeling too well the past two days and just slept. Anyway, I trust I am getting better each day so hopefully I can get to the paint mixers tomorrow and get the correct colours mixed to spray the external metal parts.

Look what arrived yesterday! A member of the happy Quad family. It has some scratches on the external faces, but at least I can get the correct colours matched.

Herman

~ To heal the soul is to embark on a new journey. ~