Philco 37-610 restoration

[jerryw22]

Philco 37-610
Day 1

My latest restoration is a Philco 37-610 radio, built in the US in the 1930's.
I prefer to restore radios and televisions that are in fairly poor condition so this was a good candidate.
My intention is to give a Day by Day account of the restoration, this of course being day 1.
During the restoration process I will take many photo's and will include some of these each day.

As you can see the radio is in fairly poor condition, probably worse than it looks in the photo's.
The wooden cabinet has lost much of its finish and the faux finish on the front is beyond saving so this will be a challenge.
The cabinet is also distored and no longer square.
I intend to keep the character of the set so will be restuffing caps etc but I have not yet decided how to approach the cabinet.

I started by removing the speaker and loose parts such as the wooden corner blocks that had fallen off.
The speaker looks to be in very good confition but I have not yet tested the field or voice coil or transformer.
The voice coil has however stuck in the armature and will not move.

I then removed the chassis and this was not easy as it had welded itself to the rock solid rubber mounts and it took some persuading.
Once removed I was very pleased to see that it was almost 100% original.
The only work seems to have been bypassing the line input filter caps which would have originally have been inside what remains of a Philco capacitor bakelite block. Most of the block has gone and the line cord has been crudely spliced and a replacement cap connected to chassis. The joints insulated with nothing more than a few layers of tape.
I assume that one of the caps inside the original block failed and blew the block apart.

Initially the presence of this block confused me as it was not shown in the service sheet but it was explained by a Philco service bulletin that details the addition of this block (Thanks to Bob Anderson from bandersentv for pointing me to that).
The line cord insulation is disintegrating so the line cord will need to be replaced.

The filter electrolytics are leaking and the chassis is fairly rusty and very dirty.

I removed all the valves and tested them, All worked but most had low emission but I intend to refit them to see if the radio works with them.

The rest of today will be spent cleaning the chassis and having a closer look at the cabinet.

Day 2 to follow...

[jerryw22]

Philco 37-610
Day 2

Today I decided to start stripping the chassis.
I intend to re-stuff all the paper and electrolytic caps so I did not bother testing these but I will test the mica caps and only replace those that are bad.

I removed the tuner assembly which comes out in one big lump.
The rubber mounts are in very poor condition so I will be replacing these.

Originally I was not intending to totally strip the chassis but it is very rusty and the only way to properly deal with it is a total strip down.

Most of the wiring is in fairly good condition but some has hardened and will crack if I try to bend it so I may need to replace it.
I heat the wires as I work on them as this makes them temporarily flexible and avoids cracking.

The main dropper bias resistor tested good.

The power transformer tests OK but I will only know for sure once power is applied.

The tuning capacitor is totally seized and will not rotate but I will get back to that later.

I spent some time examining and cleaning the cabinet, still undecided how best to deal with it yet.


Day 3 to follow...

[jerryw22]

Philco 37-610
Day 3

Time to start work on the cabinet.
Having examined it carefully it was obvious that I would need to totally strip and refinish it as well as carry out some repairs.
It was given a good clean inside and out.
The cabinet was far from square so it was gently pulled into shape. All the joints were loose and the front panel was pulling away from the main carcas.
Glue was injected into the gaps and it was clamped while ensuring it was square. The angle corner blocks that had fallen off were also gluded back in place after lightly sanding the fixing points and removing the old glue.
I then left it to fully cure and will get back to it another day.

In the mean time I got back to the chassis and continued the strip down, taking plenty of reference photo's and adding labels to some of the wires.

The rust on the chassis can be seen in the photo's so some work will be required to deal with this. It also meant that I would need to totally strip the chassis.

The IF cans were removed. The core in one was flopping around so this may well have broken a few of the fine wires that are inside.


Day 4 to follow...

[jerryw22]

Philco 37-610
Day 4

Started today by stripping the old finish from the cabinet and removing the faux finish from the front panel.
I used a chemical stripper and then throughly washed the cabinet to remove all traces of the stripper.
Then lightly sanded the front panel to completely remove the reminents of the finish.
It was then set aside to fully dry and then I would be able to more closely check the condition of the veneer.

Back to the chassis.

I removed the power transformer. Apart from a little rust it was in reasonably good condition.
On checking the IF transformers I found that one has an open circuit winding.
The fault was easy to find as it was simply a break in the wire where it leads to the terminal post (see photo).
This was most likely a result of the coil mounting nut having become loose and allowing the coil to rattle around inside the can.
I cleaned the coils and repaired the break, then cleaned and polished the IF cans.

The chassis was further stripped and the full extend of the rust could be seen.

The chassis frame parts were unbolted and removed when all components have been removed from them.

Tomorrow I will finish stripping the chassis.

Day 5 to follow...

[jerryw22]

Philco 37-610
Day 5

Finished stripping the chassis today.
One corner near the volume control is very tight and a bit of a pain to work on.

As you can see I ended up with some rusty chassis parts and a pile of wires.

I can now start cleaning and preparing the chassis for reassembly.

The volume pot tested OK but the power switch and integrated 3 position tone switch was open circuit so I will need to decide what to do with these later.

I had a closer look at the cabinet and the carcas veneer is in good shape but needs a few dings attending to.
The side and front bottom trim was removed. All had totally lost all traces of the finish.
The trim pieces were originally nailed in place but I removed the nails by pulling them through the backs of the trim pieces.
This avoids leaving holes that need filling. When I re-attach these I will only use glue.

The Dial window was removed along with its surround. This is held in place with 4 small screws. These screws had rusted and I had some difficulty getting them out.

I finished cleaning the inside of the cabinet and removed what was left of the chassis rubber mounts.

Tomorrow I will have a look at the power transformer.


Day 6 to follow...

[jerryw22]

Philco 37-610
Day 6

Power transformer.

When I originally examined the chassis I was a little surprised that a 5Y3 rectifier valve was fitted as it should be a 5Y4 and these two have different pin outs.
It turns out however that the transformer has been rewired to take a 5Y3 instead of a 5Y4.
As these can be hard to find at a reasonable price I decided to rewire the socket so that either type could be fitted.

The wires were reasonable flexible so I left these in place.

I then tested the transformer by applying power (via a dim bulb tester) and checked the secondary voltages and leakage.
All tested good so I left it powered for a while and nothing bad happened, no load of course.

It is not difficult to rewind these transformers (I have a cnc winder) but it is time consuming so I was pleased that it tested OK.

The transformer was then stripped, sanded and painted.
Once painted it is very easy to damage the paint until it has fully cured so it was put in an oven at 70C for 24 hours to speed up the curing process.
This gives a very nice and very hard finish.


Day 7 to follow...

[jerryw22]

Philco 37-610
Day 7

The cabinet got its first coat of varnish today.
So as not to bore you every day I will summarise what I intend to do with the finish and get back to this once the final coat has cured.
Coat 1 Varnish
Coat 2 Varnish
Coat 3 Varnish
Leave 3 days and lightly sand (wet).
Coat 4 Varnish
Coat 5 Varnish
Leave 5 days and wet sand until flat.
Coat 6 Gloss Laquer
Coat 7 Gloss Laquer
Coat 8 Gloss Laque
Leave 2 days and lightly sand (wet).
Coat 9 Gloss Laquer
Coat 10 Gloss Laque
Leave 5 days and wet sand until flat.
Leave to cure for another 5 days.

I use Varnish followed by Laquer as this gives a nice deep shine once the finish is rubbed out, more on that another day.

Today I rebuilt all the electrolytic caps.
The method I use is to cut the Positive terminal short and push it back into the can. Any remaining electrolyte can then be poured out.
I then use a lathe to cut the end of the cap at a 60 degree angle.
The cap is then cleaned out and the end piece given a matching taper.

The tapers allow the two pieces to be pushed together to leave a very clean seam.
This process only takes 2 or 3 minutes for each capacitor.

The positive terminal is formed using a Piece of 3mm Copper tube. The new cap leads are pushed into the tube and soldered in place.
Several layers of heat shrink are used to create the seal so that it is a good fit into the original positive post hole.
The negative is formed using the original terminal which is soldered to a flexible wire which is passed through a hole in the side of the can and then soldered to the negative lead of the new cap.

See photo's

I also re-stuffed the paper caps ready for refitting.


Day 8 to follow...

[jerryw22]

Philco 37-610
Day 8

I finally finished fully stripping the chassis and started removing the rust and cleaning it.

The power switch and tone control switch were dismantled and the contacts cleaned and re-lubricated.
The tone control is a little odd in that the common is taken through the shaft so this must be cleaned where it runs in the brass bearing to ensure a good contact. The contacts were very dirty but otherwise OK so once cleaned and reassembled both the power switch and tone switch worked well.


I checked all the resistors and as expected they had all drifted high so were replaced.

I also rebuilt the tone control bakelite block capacitor.

An old bakelite block was found and re-stuffed to replace the one that was missing on the line cord.
This also acts as a tie point for the line cord connections.


Day 9 to follow...

[jerryw22]

Philco 37-610
Day 9

Time to start re-assembly.

I began by refitting the power transformer and attaching the rear and front chassis pieces to the left side piece.
The power supply components were then refitted and connected.
This allowed me to power up the power supply on its own and check all the voltages and ensure that the transformer was OK.
I also tried both 5Y3 and 5Y4 rectifiers to ensure that either type could be used.
I had to temporarily hook up the speaker as the field coil is part of the power supply.
All voltages were OK.

The Audio output valve and associated components were then fitted.
I used a signal generator to feed a tone into the output tube,
The sound was distorted because the speaker voice coil was stuck but there was at least some output.

As can be seen in the photo's the rust has been removed from the chassis and everything given a good clean.
I decided to only partly polish the electrolytics as they still have the original printing on them which I wanted to retain.

The right chassis piece was then fitted and I started refitting the wiring. All parts were checked as I proceeded.


Day 10 to follow...

[jerryw22]

Philco 37-610
Day 10

Yesterday I got as far as refitting all the power supply components and audio output amplifier and then started to rewire the IF section.
Today I want to finish the IF reassembly so that is where I started.

I refitted the IF cans and reconnected everything. Again all chassis parts have been cleaned and the rust removed.

Once the wiring was completed I decided to check the IF stage.
I find it easier testing the radio in stages as this makes fault finding much easier.
Yesterday I had tested the power supply and audio amplifier.

On this particular chassis a temporary electrolytic needs to be fitted on the B+ dropper to prevent a huge amount of HUM.
This capacitor is normally in the tuner assembly but I have not yet refitted this.
I also temporarily reconnected the speaker as it is a field coil type and this is part of the power supply.

Powered up via a dim bulb tester and waited for the smoke but none came so that was a good.

I then carried out a quick alignment to ensure that the IF stage was working.
All coils peaked and the stage has good sensitivity although there is some instability at some points of adjustment.

A full alignment will be carried out once the radio is completely assembled.
Alignment on this chassis is very easy and only takes a few minutes.

I left the chassis running for a while and nothing got hot that shouldn't.

Tomorrow I will tackle the tuner assembly.


Day 11 to follow...

[jerryw22]

Philco 37-610
Day 11

Tuner assembly.

As I mentioned previously the tuner was seized and would not turn.
It was dismantled, and the bearings removed.
Everything was given a good clean and after reassembly it turned nice and smoothly.

I also rebuilt the slow motion drive.

During assembly I noticed that the larger of the two anti-backlash gears was incorrectly assembled.
I am assuming that this was done during original manufacture.
One of the two tension springs was only engaged on one of the gears and was causing the gear to bind and scrape on the capacitor front bearing plate. Once properly fitted (a tricky job) it turned smoothly.
It is important to remember to pretension these gears when reassembling to give proper anti-backlash operation.
If they are simply meshed with no tension then the spring tension is less than the required capacitor turning torque and the spring compresses rather than transmitting the turning force. This results in little if no anti-backlash action which makes the tuning action a little vague.

The re-stuffed electrolytic was replaced along with new rubber mounts.

The tuner was then refitted to the chassis and wired up.

I refitted the original dial (I will fit a reproduction at some point) and I was ready to carry out a first full test.

The dial was adjusted to line up with the setup marks and the radio alignment carried out.

Sound was very poor and distorted as I had forgotten about the stuck speaker voice coil.
I gently cleaned the voice coil and removed a lot of dirt and debris.
The voice coil would at least now move but it was really scraping.
I loosened the spider bolt and eased the voice coil away from the side it was scraping on and then re-tightened the bolt.
The cone now moved smoothly with no signs of scraping.
It sounded much better too but the radio still had very poor signal to noise. Stations came well and the tuning was good but there was constant background noise but very little hum.
There was also plenty of volume and the tone control works well.

The tone control on this chassis is very interesting as unlike a lot of other chassis is does not just give an 'open' and 'muffled' setting but it has a good middle setting that seems to give a good low frequency boost without causing the usual 'muffled' sound although the third position offers the usual muffling option.

Tomorrow I will investigate the noise problem.


Day 12 to follow...

[dave walsh]

Very fascinating and detailed Jerry. Thanks for posting. The mains TX and integral socket came up a treat!

Dave W

[jerryw22]

Philco 37-610
Day 12

Yesterday I got as far as powering up the radio and completing an alignment but there was a lot of noise even when a station was tuned in.
During alignment all adjustments had given a well defined peak so it appeared that the basic alignment was not too far off.
The noise was fairly consistent throughout the entire tuning range.
Touching the grid of the 6A8 greatly increased the signal level but the noise remained fairly constant.
I tried a couple of different 6A8's including the G and GT types and also metal types but the results were fairly similar.
I also tried a few different 6Q7's but again no real change.
I even tried fitting a shield to the 6A8 but this made no difference.

All the wiring was checked along with voltages but everything seemed OK.
The 6A8's all had fairly low emissions so I decided to test a few more and I found one that had fairly low emission in both sections and when I fitted it I could not tune any stations.
Before removing it and fitting another I decided to check the alignment and found it to be way off (RF and Local oscillator not IF).
After aligning the radio performed much better with better selectivity and significantly lower noise.
Obviously the radio is fairly sensitive to the performance of this valve.
I have ordered some NOS tubes and it will be interesting to see if they make any difference.
In the mean time the radio is performing well, especially considering the lack of an intermediate filter stage.

Another issue I found while carrying out the IF alignment was instability when trying to peak the IF transformers.
This was cured by dressing the wires that run through the IF stage, especially the leads connecting to these transformers.

The remaining parts were now cleaned and the scale frame stripped and painted, This was again baked at 70C for a few hours.
The paint I used was black Hammerite gloss and the manufacturers say that this can take up to a month to cure (seriously) but baking reduces this to just a few hours.
The scale is very dark so I will order a reproduction to replace it.

I like to retain as much originality as possible when restoring but one change I made when reassembling the chassis was to swap the speaker and line cord routes.
I have never understood why the line cord exits through the top of the left chassis deck and the speaker wires through the rear panel.
I routed them the other way round and it makes for a much neater appearance.


Day 13 to follow...

[jerryw22]

Philco 37-610
Day 13

Today I will be proceeding with the cabinet refinishing.

There are of course many different ways this can be done depending on the finish that is required.
The cabinet originally had a faux front panel and laqured carcase.

As mentioned earlier I decided to totally strip the carcass and front panel and start a new finish from scratch.
Over the last few weeks I have been applying the varnish and laqure.
This has now had a few days to cure so The next step is to start the finishing steps. The steps required will depend on the final finish required. I use gloss laqure even if I want a matt or satin finish as gloss laquer is generally much harder than other types and provides a very good base that can be used to obtain any finish required.

The laqure looks very shiny when first applied but lacks the lustre and depth of shine that is required. It is also very uneven and has a surface texture similar to orange peel.

The carcass and front will be finished differently so I started by wet sanding the front until it was 'flat'.
I then rubbed it out to a silk finish using 60, 240 and finally 360 mesh pumice.
More on the front panel later.

The carcass was then lightly sanded (wet) using 600 grit paper until it was 'flat' with no visible texture remaining.
This of course results in a very matt appearance.
Next it was wire wool to even out and reduce the sanding marks.
This was followed by 60 mesh pumice until all visible marks were gone.
Then 240 and 360 mesh pumice until I had a silk appearance with a slight reflective appearance.
I actually quite like this look and was tempted to stop there but I had decided to go for a full gloss finish with a good deep shine.
So it was on to the rottenstone followed by many passes with swirl removing compound.

The result was a very smooth and even finish with a very deep shine and nice colour.
It also has very good resistance to finger prints. The surface is also very hard and should wear well.
If I ever change my mind and want a silk finish I can always go back over it with 240 and 360 pumice.

The shine is very deep and hard to photograph.
(comments welcome on this).

The next step is the front panel.


This may take a while so I will post the next update once it has been completed.

[Herald1360]

Originally Posted by jerryw22

Philco 37-610
Day 1

My latest restoration is a Philco 37-610 radio, built in the US in the 1930's.


The line cord insulation is disintegrating so the line cord will need to be replaced.

...........

Line cord? Does that mains transformer only have a 115V primary?

Line cords are normally only found on series heater AA5 type imported sets.

[jerryw22]

Herald1360

Yes it has a 117V primary but is not a series strung set. It has a secondary for the heaters (and of course one for the rectifier).
I will rewind it at some point for 230V operation.

Jerry

[crackle]

I am dying to see the cabinet. Photo outside on an overcast day.
A few reflections only help to emphasise the shine.
The chassis is looking good so far.
Mike

[jerryw22]

Mike
Thanks, I did try to photograph it but they did not come out very well, too many reflections. I did not think of trying it outside so will give that a go.
I was surprised how well the cabinet came out. It looks terrible in the original photo's but after stripping it was actually in really good condition with a very even colour and no deep scratches.
The cabinet actually took several times longer than the chassis.

Jerry

[Oldelectronics]

I am realy enjoying this thank you for the post.

Kev

[Yarraman]

Great job Jerry. On a Philco 38-10 I have, the valve shield bases and hence the shields were not earthed due to corrosion between the chassis and the shield base which caused a bit of instability in the Radio. I had to drill out the rivits holding in the valve sockets etc, clean up the area and remount them. I also had problems with the Antenna coil, which I replaced. look forward to seeing your project finished.