Howard Valve Radio, Let's make it sing again. - Page 1
Forum section: electronics / repair

author: Muttley Snickers
author_rank: Unknown
timestamp: July 08, 2016, 04:38:31 am
content: Recently we had a hard rubbish collection whereby residents put out on the nature strip all manner of unwanted goods and the local council eventually comes around with a big rubbish compactor and the goods get destroyed and discarded without reservation. I happened to be driving along on the way to a job and noticed a lady and her son struggling with a large timber antique cabinet down their driveway so I stopped to lend a hand, coincidentally the cabinet they were throwing out was very similar to one we already had in our dining room which was acquired from my late grandparents estate.They were very grateful for the assistance and I mentioned that I had almost the same cabinet back at home and it was a shame to see their one destroyed, we conversed for a while and they invited me in to the garage to show the other items that they intended to discard one of which was the Howard valve radio pictured below, the lady explained that her late husband started to restore the radio by replacing the speaker grill and giving the unit a fresh coat of varnish but he could not get the unit to operate, she openly invited me to take both the cabinet and the radio and agreed that the destruction of these units would be a shame but they had little choice in their current circumstances, the lady and her son both indicated it would be a pleasure to hear that I was able to get it going again hence my post here.I have no knowledge of valve radios and have searched the web for information and did find these couple of links below, one with a list of Howard radios including pictures and schematics but at this point and after a thorough look I cannot determine which model it is, the unit powers up with lights illuminated and I can get the speaker to thump mildly if the far left knob being the tone control is rotated, I simply don’t know where to start on this one so any assistance would be most welcomed. The other larger wall cabinet is currently covered up on our back verandah about to be stripped down and a fresh coat of gloss polyurethane applied, I’m just waiting for a good dry day to get that one underway with no electronics involved on that project just plenty of elbow grease.Once again, thank you all very much for your guidance.Radio Museum.http://www.radiomuseum.org/m/howard_usa_en_1.htmlAustralian Vintage Radio.http://thebakeliteradio.com/page102/page102.html

author: GEuser
author_rank: Frequent Contributor
timestamp: July 08, 2016, 04:49:37 am
content: If it was me , 1st pull the chassis and replace every electrolytic , then start from there ..Nice looking , basic chassis , looks like no ShortWave so it's absolutely useless (tis a joke) .

author: lowimpedance
author_rank: Super Contributor
timestamp: July 08, 2016, 05:02:41 am
content: Absolutely replace the electro's (including those chasis oneson the left!). It appears to be missing the 6v6 which I suspect is the audio stage output.With the chasis out for the caps also look at any wax diped paper caps and replace those too. Check the value of the carbon resistors which generally drift high.When powered up breifly did you notice if the existing valve heaters were glowing or not. Watch out for the B+ HT rail can be 'bitey' at around +200V DC.Also Check the mains transformer is not 'leaky' from its windings to the laminations. The volume pot will need a good clean and also you might need to give the tuning gang some TLC too if tuning is an issue.Nice case so even use it as a static display if the restoration of the chasis is not sucsessful.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 08, 2016, 06:00:29 am
content: Thanks very much for the information, I needed somewhere to begin and as GE mentioned a handy start might be to get the chassis removed from the cabinet to have a proper look which I have now done without damaging anything else, also you blokes might be right about those capacitors as they do look slightly buggered, a big hairy spider hiding in the corner didn't help much either.Overall the whole thing looks a bit crusty but if I can learn something from the experience then I will be more than pleased, funny thing is a few mates have already seen it and all put their hand up to take it providing the radio works, I'm keeping the unit regardless as it matches another valve radio/ turntable cabinet I also have which does work well.I'm not sure if a valve is missing as there is an empty socket, either way I will start cataloging and removing the paper caps and whatever else looks to be problematic, once again much appreciated.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 08, 2016, 06:41:49 am
content: Looking at the last pic there are connections and components on the 'empty' socket so I'd reckon its missing. It looks like the RF, IF/detector and rectifier tubes are present but not the audio stage.Best to list the type numbers of those present too, but be careful of the print on them after all these years it rubs off the glass very quick with the lightest of touch.(I think the octal base types had there part numbers mostly on the bakerlite base.......IIRC).That aftermarket mains connection has got to go. Add a fuse and proper strain releif etc.Appart from some rather crusty caps the underside looks generally quite good. The silver mica caps are the brown rectangular ones and usually are still good.Those big resistors color codes are fun to interpret.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 08, 2016, 06:45:07 am
content: Just a few more freehand shots and some might be doubled up which I will come back and fix later, only one valve lights up very faintly and the main station display is out one globe and looks rather sad to say the least, not critical about this as there is not much I can do about it at the moment.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 08, 2016, 06:53:45 am
content: At least the 6.3 V heater winding is good as the backlight globes run of it as well as the valve heaters. The valve glowing looks like the rectifier supplying the approx. 200V dc.Look up the type number, plenty of info online for pinouts etc so you can see if the HT is there. But best to do that after a recap with appropriate new parts.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 08, 2016, 07:10:05 am
content: I will have to get back on to this over the weekend, all the benches are full of ongoing stuff some of which I can't move or touch which is a real pain, also for my own record I want to take some better pictures with improved lighting for future reference, many thanks lowimpedance for your wonderful assistance, I owe you big time.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2016, 07:39:34 am
content: There can be a few traps in these old girls, eg. the rectifier tube heaters are often 5 VAC from a dedicated winding and all the others from a 6.3 VAC winding that is capable of much more current that the 5 V winding. This heated cathode setup begs for respect from the HV imposed on it. The HV AC supply from the transformer is a often center tapped 500-800 VAC secondary that when rectified and smoothed with a LC or CLC. Not a lot goes wrong that has them NOT working....OC or shorted chokes, OC resistors, coupling caps, OC primaries on the audio output transformer and open heaters on tubes. Buggered pots, drifted resistors and sick caps often still have them working, just not well.Good luck Muttley.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 08, 2016, 10:58:55 am
content: Ah yes , important note regarding the rectifier. These old timers need to be given all due respect when poking around !.

author: GEuser
author_rank: Frequent Contributor
timestamp: July 09, 2016, 02:43:12 am
content: Good pics also a very clean unit underneath for it's day too , Also when electrolytic's which i mentioned those paper caps are also included in that terminology as all they are is paper wound "with" a electrolyte also , I'm not picking at anyone just stating that they are the same whether paper or not ok , = so no confusion .Yes be careful poking around for sure , the audio out transformer is actually on the speaker so watch those wires could be around 250Vdc there .If your looking for a schematic look/search for any generic tube set , I'd suggest looking or searching with the Valve (Tube) lineup as you'll be surprised just how similar they were back in the day (for the same amount of valves) over many brand names and models some with slightly altered areas or major altered areas , I'm typing about the copying syndrome back then ! so it's not a new thing , should see the valve TV's too .After one has sorted out the Caps , one then can poke around with a MM for quick resistance checks and the likes still not fired up or plugged in , fit a fuse as LowImp suggested and go from there , if one gets it actually all lit up do use a Analog MM poking around especially around the Grids .But it's all a waste of time though imo as it has no ShortWave ha ha ha ...have fun cheers ..edited>spelting

author: poot36
author_rank: Frequent Contributor
timestamp: July 09, 2016, 03:05:45 am
content: I would start by making a dim bulb tester to reduce the current drawn by the unit in case of a fault. I would start by removing all the tubes except for the rectifier and then use the dim bulb tester with a 40W incandescent bulb and carefully measure the B+ voltage out of the rectifier tube. It may not get to normal operating voltage but that is ok for now. If it is a safe voltage for your oscilloscope to test also check it for ripple. I have seen radios from the 40s that have all original caps and still work fine. I would also check out the Antique Radio Forum here:http://antiqueradios.com/forums/index.phpand BAMA:http://bama.edebris.com/manuals/.Is there a name plate or maybe a model number stamped somewhere on the chassis?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 09, 2016, 03:19:12 am
content: I have also had some pretty good luck with old caps still working. But the advice to replace them is good, they do have a high failure rate at this age, and failure can be spectacular, taking other stuff that is hard to replace with them.If you do choose not to replace it is best to initially power the set with low voltage to allow the electrolytics to reform. Most of this era had wet electrolytes, and often had far more moisture in them than required. If the seals worked well enough they will heal the actual barrier layer. There are lots of recipes for the voltage and time applied, but nothing is perfect. Low and slow is the only good general advice, and don't count on success.If you do replace them, I like to keep the old casings and put the new capacitors inside. It retains the old look of the radio. It does require care. The stuff inside is not good for you.

author: GEuser
author_rank: Frequent Contributor
timestamp: July 09, 2016, 03:26:27 am
content: Quote from: poot36 on July 09, 2016, 03:05:45 amYes you can do that of course , look if you know what you are doing and know how to use a Analog MM one does not need too as the MM will tell you exactly what is happening anyway and is far quicker .And yes caps can still be ok but that is not the point , a quick turn on then off that's fine the caps are ok , leaving a valve radio turn on (listening or whatever) for 6 hours or more is really pushing the luck for 40-50 year old Electrolytic's (safely) , these days good electo's can fail at 10 year or have much reduced parameters , those old paper ones certainly did reduce in parameters but also when they failed they got to sound like a Fizzer and do/did regularly .So the point is , for the sake of a bit of time and a bit of expense and if it was something that might actually get used for some hours or more daily or weekly , replacing all electrolytic's is a necessity for a peace of mind , imo of course and it's not as that info is new either .

author: rsjsouza
author_rank: Super Contributor
timestamp: July 09, 2016, 03:36:37 am
content: Muttley, being an AM-only radio simplifies things a lot - in multiband radios the band selector switch is terribly difficult to trace.Also, what helps is that several of these heterodyne radios have more or less a simpler schematics to get by: one or two IF stages powered by heptodes (less coils to go bad and require trimming), followed by a stage with dual functions: diode (for AM envelope detection) + tetrode/pentode and, at last, a pentode to drive the audio. Check the attached simple schematics (sourcehere).

author: GEuser
author_rank: Frequent Contributor
timestamp: July 09, 2016, 03:37:33 am
content: https://en.wikipedia.org/wiki/6V6

author: GEuser
author_rank: Frequent Contributor
timestamp: July 09, 2016, 03:44:26 am
content: Quote from: CatalinaWOW on July 09, 2016, 03:19:12 amThat's those on top of the Chassis in the cans i gather just for muttly's sake , all those others underneath are not seen so it does not matter right?

author: tautech
author_rank: Super Contributor
timestamp: July 09, 2016, 03:48:04 am
content: IMO those caps under the P-P tag strips look the most suspect.

author: GEuser
author_rank: Frequent Contributor
timestamp: July 09, 2016, 03:57:26 am
content: Quote from: tautech on July 09, 2016, 03:48:04 amThat's the trouble with those old things , one can not go by looks alone , the most obvious look fail is if even a slight looking substance is at the end (positive) as that is the electrolyte leaking out , over the years real good brand new looking ones have been the worse .CatalinaWOW also brought up something too , that is when they do Fizz out all that stuff can go everywhere and is corrosive , the ones i have seen detonate leave paper fragments all over the place and also are corrosive so he is correct in typing that they can damage other components which might be hard to get or troublesome .

author: rsjsouza
author_rank: Super Contributor
timestamp: July 09, 2016, 12:08:34 pm
content: The vacuum tubes I guess from your pictures are:-6U7Ginside the round metal can on the center of the radio-6G8Ginside the round metal can to the right-6V6GmissingFrom the pictures I guess the following:I can see the radio is set to 240V input (out of 220 and 260) and the filament/cathode of the dual rectifier is tied to the two orange wires. The AC +B (high voltage) output leaves the transformer on the two green wires that are connected to the rectifier. I may be wrong, but the 6V that supplies the filaments of the other vacuum tubes leaves the transformer via the brown wire - the other leg may well be the chassis (black wires leaving the triple tie point on the transformer).The two small capacitors (8uF and 16uF) are oddly far from the rectifier, but they are sure the +B main filter. As others suggested, I would desolder the + leg (the - leg is on the chassis) and check them thoroughly. These things tend to live a long life, but you never know.The yellow capacitors at the bottom of the IMG_0498.jpg seem to either have been bathed in rosin or are leaking.The charred capacitors in IMG_0500.jpg seem fine, although they are most probably wax paper capacitors that may lose capacitance over time. I would test and/or replace them.The yellow capacitor at the right side of IMG_0500.jpg seems to have been bitten by a mouse. I would definitely replace it.Leave the tube ceramic capacitors alone, as they have a very long life.Also, a lot of the adjustments on these radios was done by careful positioning of the components. When desoldering, I would be very careful not to spread components too apart from their original positions.

author: N2IXK
author_rank: Frequent Contributor
timestamp: July 09, 2016, 02:52:51 pm
content: I repair/restore a LOT of tube-era gear, and a complete replacement of paper and electrolytic caps is almost always called for. Materials science has come a LONG way since these things were made, and modern plastic film capacitors will last a LOT longer than the old wax dipped paper ones did. If you test the paper caps at anything even close to their working voltage, they will be found to be almost universally leaky to some degree. The electrolytics are usually dried out and exhibit high ESR and excessive leakage. A modern ESR meter or DMM capacitance function isn't very useful for checking these caps, as they only apply a few volts to the cap under test. Replacement caps are cheap enough that this is one of the few places that I ever recommend "shotgun" replacement of parts. Only the electrolytics and paper caps need replacement. Ceramic and mica caps age much more gracefully, and should only be replaced if found defective by testing.Looks like a nice set, and well worth restoring. Good luck with it!

author: Cubdriver
author_rank: Unknown
timestamp: July 10, 2016, 01:19:00 am
content: Muttley -That looks like a directly heated full wave rectifier tube adjacent to the power transformer. If so, it will have its own private filament winding (likely 5V) which, when the radio is on, will be sitting at B+ (likely 200 or more volts DC). It appears based on the labeling on the rear of the chassis that you're missing the audio output tube (the 6V6 marked at the rear chassis corner). The radio will be rather quiet without this particular tube in place.As others have mentioned, paper caps have likely become leaky over time, and electrolytics may well be completely dried out and defective.I'd start by securing a 6V6 and installing it, then turning on the set and baselining it - see what it does before you delve too deeply into it. Don't be surprised if there's a loud 2x powerline frequency hum/buzz that is there regardless of the volume setting - that's in indication of dried out or otherwise bad filter caps.If you decide to re-stuff the can electrolytics, you can see photos of my first two attempts here:https://pmanning.smugmug.com/Electronics/Restuffing-can-electrolyticsThe first starts is at the beginning, and the second starts at photo #27. I changed the way I re-formed the crimp on the second (rolling it on an aluminum plate till it was most of the way done then tapping with a hammer at the very end rather than using hammer blows for pretty much the entire bending of the lip), and it turned out much neater than the first.First crimp re-form (hammered) final result:Second crimp rolling:Final forming of second attempt with hammer:End result for second cap:I wish you success in getting the grand old girl back up and running!Best-Pat

author: Muttley Snickers
author_rank: Unknown
timestamp: July 10, 2016, 02:13:30 am
content: Thanks Cubdriver, we might be in a bit of luck for a change.Unfortunately I suffered with a migraine for most of yesterday and didn’t get much achieved at all and today is not looking to be much better, I did have a brief closer inspection of the unit and quick look at some of the links provided above which I am very grateful for, I will need to study these pages more when the eyes stop flickering.A bit of the existing wiring and number of solder connections on the unit are questionable and will require attention as well there is no mains power switch incorporated on any of the potentiometers and I may also look at addressing this as I do have a collection of switches and other switched potentiometers, the mains and fuse situation as previously pointed out without question needs to be tidied up but I am not sure if the chassis is meant to be earthed, our existing valve radio does have continuity between the mains earth plug and the metal chassis depending on where you probe, brass fixing screws seemed to be the best place.I might be a bit lucky here as our existing valve radio appears to have onboard one of the valves that is currently missing from the Howard which I will probably need to test with and was labelled as a 6V6G on the chassis, the other existing valve on the Howard was a 5Y3G and appears to be in good order, others might be able to confirm if this is a good idea and the old radio had in fact two 6V6GT/G valves both of which were very similar and pictured below.Once again many thanks to all for the great advice.

author: tautech
author_rank: Super Contributor
timestamp: July 10, 2016, 02:24:15 am
content: Quote from: Muttley Snickers on July 10, 2016, 02:13:30 amThey generally are Muttley unlike old TV sets that have a live chassis.Quote5Y3G = Full wave rectifier6V6 = Beam Power Amp6N7G = Class B Twin Triode6SQ7 = Duplex Diode + High MU TriodeI've got an OLD book with the specs for these if you need anything photocopied.In fact I've got a bit of selection of old valves should you need some.....if I can find them.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 10, 2016, 02:59:51 am
content: It works.I just dropped in one of the 6V6G valves from the other radio and connected up a long wire for the antenna and gave it some juice, the unit fired up with the sound of white noise so a slight fiddle with the tuner gave me a few radio stations, all of the pots are bad and causing crackle and after a minute or so there was a faint burning smell, nothing dramatic just enough for me to pull the plug and think about addressing some of the issues at hand.A stroke of luck, we are not done yet by any means but certainly a good sign of things to come.

author: Cubdriver
author_rank: Unknown
timestamp: July 10, 2016, 03:01:49 am
content: Muttley, it looks like your big Howard has a push-pull output stage (the (2) 6V6s being the power tubes and the 12SN7 being used for the phase splitter to drive them. The 5-series tube is the rectifier in both sets.Do they mount the audio output transformer on the speaker frame rather than the chassis? I see only one transformer on each of the two different chassis, but one of the photos of the 'new' radio shows what could be a transformer on the speaker.The 6V6 is a popular output tube; it's likely that someone pilfered the one that was in the new radio at some point in the past. Either of those in your old set should work. The suffixes on American tube numbers typically designate revisions and areusuallybackward compatible, electrical-wise at least. The 6V6 was developed by RCA, and initially released as a metal tube (the plain 6V6 designation). At some point, a glass envelope version was introduced (the 6V6G, popular lore seems to be that the 'G' stood for glass; these were the early 'coke bottle' tubes with the shouldered envelope and are physically larger than the original metal version and so may not bephysicallybackward compatible with it but if they fit they'll work in place of the plain tube. Next came the 6V6GT, this being a physically smaller version with a tubular glass envelope (Glass-Tubular being the explanation I've seen for the suffix) rather than the original shouldered version of the 'G'. This was eventually followed by the GTA version, the 'A' designating some additional characteristic of the tube such as controlled warm up filament for use in series string arrangements or some other sort of improvement.TL/DR - the 6V6 in your big radio will work in the new radio.Hope your migraine passes soon.-Pat

author: Cubdriver
author_rank: Unknown
timestamp: July 10, 2016, 03:03:58 am
content: Muttley - just read the post you put up while I was working on my last one. Excellent - glad to hear that it at leastsortof works! Fingers crossed that whatever caused the burn smell is minor.-Pat

author: tautech
author_rank: Super Contributor
timestamp: July 10, 2016, 03:09:15 am
content: Careful Muttley your new boombox might give you a real headache now it's going.I dunno, these young fellas and their boomboxes.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 10, 2016, 03:16:56 am
content: Just tried it again and no joy, whatever was causing the smell which I can only describe as slightly waxy if that's a term has caused the unit to stop responding, so as previously mentioned time to start getting a list together of required components and fortunately for me a good friend only five minutes away is a retired TV repairman with bins full of older components including capacitors, some of the values of which I certainly wouldn't have around here.

author: Cubdriver
author_rank: Unknown
timestamp: July 10, 2016, 03:27:13 am
content: Sounds like (other than letting the magic smoke out) you should be in pretty good shape, especially with the retired TV guy's assistance.Keep us posted on your progress.-Pat

author: vk6zgo
author_rank: Super Contributor
timestamp: July 10, 2016, 03:53:12 am
content: Quote from: tautech on July 10, 2016, 02:24:15 amLive chassis BW valve TV sets are very,very rare in Oz---They almost all used a power transformer.The only exceptions I can remember offhand were a few early "portables" from Admiral,& perhaps Stromberg-Carlson,or Healing.Maybe the situation in NZ was different.Some country towns still had DC Mains in the '50s,so some AC/DC mantel radios were built for that market (pretty much as "special orders").Apart from those few,the "all-American Five" style of AM radio & its Brit & Euro equivalents never took off in Australia,as transformers were cheaper to make in this country than the extra insulation needed with transformerless construction,to say nothing of series string valves.AWV & others turned out enormous quantities of normal 6v & 12v heater valves,& very few other types.In any case,transformerless designs were very much frowned upon by Electrical Authorities.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 10, 2016, 04:29:45 am
content: Quote from: GEuser on July 10, 2016, 04:03:30 amI worked at Atkins (WA) back in the day----I was only a storeperson with apirations at the time.Whenever one of those things came in to go to the Workshop,everybody shuddered.One thing which I remember from that time was that Atkins were agents for AEI,who were selling Radios & TVs under the Ekco brand--All nice sets,& pretty much standard OZ style,despite the UK origin of the name.The RM204 was a normal 5 valve mantel set,& the Workshop guys discovered the RF & IF stages would work OK with 32vDC HT,but the output stage was a bit lacking.They replaced that with a transistor output stage,& changed one of the valve stages to a 12.6 v filament type.Quite a few of these were sold to farms with 32v DC lighting plants.I'd love to find one--a definite collector's item.

author: SeanB
author_rank: Super Contributor
timestamp: July 10, 2016, 10:44:29 am
content: Time to replace all the wax capacitors before any more power being applied, as you can very easily blow a screen grid on the valves, or burn out the transformer with a leaky capacitor. As well replace all electrolytic caps, especially the 100uF 16V ones on the cathodes, though there use a 63V part, as it will be the same size as the original.then you can go resistor checking, mostly in circuit as they pretty much all have vacuum on the one side when power is off. If higher than the nominal value simply replace with a new 1W film for all, except for power resistors where you need a higher rating. 1W film simply because they are similar in size and have a high enough voltage rating so will not flash over or burn out.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 11, 2016, 02:49:28 am
content: Thanks Sean, yes after the sausage sizzle we experienced yesterday I wont be powering the radio up again until it is good, safe and ready to do so, I'm still having no luck finding the main PCB and microprocessor and thought they were hiding somewhere out of sight so this is now a mystery, it couldn't possibly work properly without them surely.I had a bit of difficulty de-soldering a few of the existing condensers and didn't want to just cut them out in case they are still ok or if I cannot readily get hold of replacements, simply not enough tip area on the bench soldering irons to transfer the heat into the old connections, most of which were back onto the chassis itself so I resorted to the Weller Gas Pyropen which is always excellent for larger solder pads and these types of old crusty joints, it worked a treat.The far left red capacitor in image 0517 was not connected at the displayed end and the remaining exposed lead appears to have been either cut, corroded or simply broken away, it's very hard to determine what occurred there but we did have the radio sort of working for a short period without it so I don't know about that one.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 11, 2016, 04:06:50 am
content: The one on the right in the first pic looks like the offending sausage(not sure the aroma would have been as inviting as the more traditional BBQ!).Its good to see some more 'vintage' stuff here, particularly when most of the time all we get is micros, LCD's and highly integrated PCB's .......yawn.

author: SeanB
author_rank: Super Contributor
timestamp: July 11, 2016, 04:53:22 pm
content: Do not try to unsolder the leads from the tags, just cut right by the body, and replace with polyester capacitors of the same ( or the next value up for those oddball ones) capacitance and with a higher working voltage. The lead stubs make fine ends if you use a small pair of needle nose pliers to make a loop to put the new lead through then solder in place. Same for resistors, much easier than trying to get solder off a brittle base that will crack if heated or moved too much.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 12, 2016, 11:58:19 pm
content: I'm going to start cutting the majority of them out this afternoon and have been taking a number of close up shots so I will know exactly where they were connected when putting them back in, a couple of closer pictures below of the main suspects, one looks to have been chewed by a rodent, another looks to be suffering from leprosy and the final one blew a fuse or something.