Tuesday, 29 November 2011

Postie was busy today... lots of parts

Amongst them ...

25uF 400V caps for Sussex valve tester and a new paraset inspired RX only for 80m (I will have to camouflage them to look like Sprague caps)
Rapid order for all the other Sussex parts (except, chassis, transformer, PCB and meters)
Farnell order for the Phasianus colchicus (481THz rxtx)
A couple (one spare) 74HC14 for the ESR meter.
Some PIC-A-STAR parts that have been on back order for a while
Some TI and AD sample chips.

I guess I am going to be melting solder later....

Sunday, 27 November 2011

ESR meter - update

I also just built the VE7IT/G4EBT/http://www.vintage-radio.net/forum/showthread.php?t=54367&highlight=esr+meter version using vero board layout.

I didn't have a resistor network for the 5 680ohm resistors so I just made one up from 5 discrete resistors.

The circuit calls for a 0.47uF 400V capacitor which provided high voltage blocking/protection in my case is a 0.1uF 630V capacitor. I have a couple 0.22uF and a 0.33uF as well but only to 250V and 275V.

The three 10nF are 50 V the others are either 63V or 100V.

I have to laugh though... I thought I had some Logic 74HC14 IC... well that is what I should have had... what was in the tube in fact were 74HC04 ... oh dear.

I think this meter might be suitable for conversion to a PIC with an LCD readout as it is a simple AC ohmmeter. The signal is applied to RA1 or whatever of a PIC and sensed. I might play with that some more.

The other meter I built earlier I'm going to to box that up this afternoon, along with a simple 555 based 1KHz oscillator.

I was sent this note as my FSD is 44uA.

> Problem right now is the FSD I replaced R17 with 1K8 and pot is at zero and still get no >more than 44uA. I used a 2N2222A.

That's odd. In mine, I used a 3k3 fixed resistor as R17, and a series preset 22k pot to zero the meter. Using a 50uA meter, with the cap test leads shorted, I had no difficulty getting the meter to zero (right hand end of the scale). Yyou've obviously had a poke around with your scope, and might like to check the readings against the following:

From the junction of R8, D5, D6 and C5, there should be a waveform of about 180mV peak to peak, but it’s important to note that this is only when the test leads are shorted, or a good cap with a low ESR is connected to them. This AC waveform then passes via C2 to the base of the 2N2222A which is an AC amplifier with a gain of approx 10.5. It's role in life is to raise the 180mV p-p input to nearer 2 Volts p-p. This then passes to the meter rectifier D1,2,3 &4, for the meter movement. But without the test leads shorted, or a known good electrolytic cap with a low ESR attached to the test leads, there will be zero Volts at the input of the 2N2222A, nothing at its output, so no deflection on the meter. The meter rectifier enables the meter to function as an expanded scale AC voltmeter. Full scale is zero Ohms, midscale is approx 10 Ohms. There is no DC output until approx 75 Ohms of ESR is seen at the test terminals, (ie, a bad cap), at which point the meter will barely deflect.

(The role of the cap C5, stated as 1uF in the VE17T original article but shown on his board as 0.47, is to protect the meter should it be applied across a charged cap. It doesn't have any bearing on the functioning of the meter).

Saturday, 26 November 2011

Valve testing.

This is an exchange I'd like to share from the G-QRP email list that some might like to read as it contains some information that I found of use...

Hi Dom,
I cannot offer either a valve tester or some spare valves, but the following might help you to cope without a tester..
My working life started in 1957 as a MN Radio Officer, so I cut my teeth on valves.   Ships were not supplied with any means of testing valves as such, but We managed adequately without.   Generally there are two main types of faults with valves.   Either the heaters goes o/c, or the cathode emission reduces.
An o/c heater is easy to check - either there was a lack of glow in the glass or, if necessary, the test meter can be used!
Low emission can be determined by the valve clearly not conducting as much current as it should, determined by "wrong" pinout voltages.   The tests are relatively simple.  
First check that h.t. is correct.   At the time, being too low usually indicated either valve h.t. rectifier gone low emission or a vibrator with burnt contacts. (Ships of the 1950's commonly had d.c. supplies, or possibly the receivers were run from the 24v energency battery supply - hence the need for the vibrator).
Assuming the h.t. was correct the next checks are voltages at cathode, screen grid and anode.   Assuming there was some resistance in series with the pin, either cathode volts low, or screen and anode volts high can be taken as general indications of low emission.
The next test was simple to a seagoing "Sparks" - try a new spare valve.   Fortunately the "Merchant Shipping (Radio) Rules" dictated that spares were carried to a minimum quantity calculated by a defined schedule.   If found faulty, the offending valve was left to swim home!
In some equipment, I have in mind particularly the magnetron in the radar which operated on a very low duty cycle - short high intensity pulses at relatively long intervals, the manufacturer actually wired in a series resistor, duely shunted by a suitable smoothing capacitor, with the handbook stating the correct voltage drop for a valve having normal emission.
If you want to make a tester, don't get too technical as it isn't necessary.   Uswe the heater and h.t. supllies from any suitable piece of kit you have and using a spare valveholder wire up the base with suitable values of anode, screen and cathode resistors to vause the valve to conduct a modest amount of current, that is well below full dissipation rating for the valve in question.   Measure the current with a milliameter in the cathode circuit (it keeps h.t. from both your fingers and the meter movement).  Record readings of anode current, screen voltage and cathode voltage.   The voltage at the cathode is in effect the same as the negative voltage at the control grid.   Because the cathode is at a few volts above zero, remember to subtract this voltage from the readings you get at anode and screen grid.
Now compare what you get to the characteristic curves for the valve in question, remembering that is the valve was from a "Quality" manufacturer, you can expect the actual characteristic to be within about 5% of the publlished data.   If you are getting anode current readings substantially lower than you should for the values of grid (cathode), screen and anode volts, then the valve is low emission.
If you need valve characteristic curves, feel free to ask, as I have quite a lot of valve data books.
I hope this helps.
Alan   g3rmz  in Plymouth

From: DomBaines
To: GQRP@yahoogroups.com
Sent: Friday, 25 November 2011, 12:02
Subject: [GQRP] Valve tester anyone?

Hi all,

Anyone got a valve tester capable of testing the metal 6??? series of octal tubes 6K7, 6J7, 6SQ7, 6V6GT (OK this one is glass)? Either I could borrow or I could send you the valves and you test them for me? Or I could travel to you in person if local to me... I am in Cambridge and not working right now.

I can test if the filaments/heaters are intact with a meter but that is about it and want to know if any of the valves in my HRO-5 are duff or not. I think most are fine and the AF and IF sections seem to be working, the LO seems to be creating a signal as you can pick it up with a MW radio but it is still not working and the signal is lost in the mixer but not really sure.

The PSU heaters are fine, the HT is fine, the capacitors and resistors seem to be testing fine (although building an ESR meter to confirm that)

Or anyone advise a simple series of tests I could do? I'd feel a bit stupid shelling out for a valve only to fine the original is fine.

I have also thought about trying to build one :-)


Or...a nyone built 'The Sussex VT' valve tester? or got a part build they can spare.



The Sussex VT1 - Valve Tester

I'll be building one of these.

See the whole thread here http://www.vintage-radio.net/forum/showthread.php?t=48853 this includes all the details of the build and part sourcing.

I have the PCB coming, parts on aorder, ebay orders out even to hong kong and USA and someone is winding me a transformer. So I might have a test set.....

Now just to create the tables of values for the valves I am using... so will be in the workshop and shack later creating an inventory of them. I suspect a little like Richard G3CWI talk about a VNA in the workshop at Rishworth GQRP 2011 conference, I might end up testing/measuring many of the valves I use rather than building something with them :-)

I'll post images as the build progresses.

HRO-5 underside

I've been asked to post more images of the underside of the HRO-5 set so here you go...

Some of the components  might 'look' like they were from 1943 but they hide a secret... A number of the Sprague capacitors were literally rebuilt (not by me) and house a modern value inside, the old capacitors were suspended (in an oven I think) until the wax seals melted and the contents fall out, then a new capacitor was inserted and the ends resealed with wax.

There are two visible modern resistors (one is 1/2W other 1/4watt) but the rest are originals that were not 'high'.

The wiring loom was 99% sure completely replaced with new 'look-a-like' cloth covered wire as the original had degraded.

Phasianus colchicus

Today whilst out dropping off something at a friend of my wife I was looking for a suitable location for operating at 481THz (optical) and the car right in front of me was hit by a pheasant flying across the road. The car never stopped but the pheasant ended up in the road side about 50 yards ahead of me. Dead obviously. So never one to miss an opportunity I collected it up and the pheasant will go into the pot.

UK law is great in this regard... if you knock something down, technically, if you pick it up, you could be accused of poaching but I suspect very unlikely to be so. However, if the vehicle in front of you knocks something down you are perfectly able to pick it up without fear of prosecution. The Law Is A Ass according to one of Dickens characters so things don't change do they?

Irrespective of the death wish pheasants appear to have around here...this has inspired me to call my opto TXRX build 'Phasianus colchicus', or Common Pheasant.

Some of the following images might not suit every one so if you are not into preparing game then do not read on.

 Plucking, start at the head ...

I'll not post the more gruesome images after this one....but this is where food comes from and I was brought up in the country and every time I do a long cycle trip it is amazing what you can pick up and roast on an open fire.

The RXTX circuit and images will follow.

Friday, 25 November 2011

Valve tester - homebrew

See my later post about the Sussex VT1 - Valve Tester as that is what I am building.

I have a need to test some valves but no real way (idea) how to do it so as well a checking some old manuals but they mostly just said plug the valve (or tube if was a US book) into the valve tester and check emission etc..... really helpful! So I did a google search brought up a couple of testers that cost more than my whole shack and then I came across this basic circuit which seems really simple. The 2SB546 is a high voltage PNP power transistor I might see what I have that might suit. The comment is any PNP with a Vce of 200 volts or higher. Beta is important here though. It determines the size of the bias resistor (39K 1W). The specified 2SB has a measured beta of 250. The suggestion is to use anything over 100 and preferably over 200 to keep the R small.

You connect the valve pins for K,A, G1-3 and filament to where they are on the above diagram.

It was for a 120V (US) mains supply so I have a UK 240V isolation transformer or a UK-US step down transformer I can use.

The notes on it are:

It can do both an emission test and grid-shift.

For straight emission, just ground-out the g1.

Because the CCS makes for a high plate-Z, it's prone to becoming an oscillator. The 25uH choke in the plate lead solves that.

No need to filter the supply, which simplifies things and the pulsing DC keeps dissipation very low.

The optional grid-shift tests statically the tubes ability to bias. Can also be used to match tubes (for DC characteristics). Nice compromise between simple emission tester and full-blown transconductance tester.

An additional note says:

But, why not tie g1 to the plate and g2 like other testers? There is a problem with this, as shown here

Now I realise I might also need to do something like check the amplification but that comes later maybe. Would be interested in any comments.

More info (from the guy that shared the info  http://geek.scorpiorising.ca/GeeK_ZonE/index.php?topic=1803.80 called Gregg) follows this is the full circuit:

This is gonna need explaining. First I'd like to say, keep using the shaver transformers for the HV section as we have outlined in the past. You will need two, one to supply the plate (unfiltered), the second in half-wave for bias and short test. The only reason I've used the cap-filtered version here was to try and simlify the power supply. When I did this before, I eneded up with blown transistors due to the current surge from the cap. The 560 ohm, 5 watt and 330 ohm, 2 watt in there solves the surge, but there are two drawbacks:

- We lose out 100mA scale
- Junction heating above 30mA does cause "creep" in the current.

Why I didn't revert back to the old version of B+ supply is I had already assembled the transformer I wound for it and didn't want to take it apart again

Fusing, use fusing. There are three here, one for the primary, one inline with the CCS (Murphy will make sure your Mullard EL34 will be destroyed to protect the primary fuse if all hell breaks loose) and the fuselink in the ground of the high current transformer CT. I made that from a 6" or so piece of #30 or 32 wound on a drill bit. It changes color at 3A and glows slightly at 5A and can handle the cap-charging surge better than a real fuse. It severs, the whole filament side shuts down

I had a bugger finding 12V DPDT relays for under $10, so I used some 6V ones the local electric place had a surplus bin full of and added a big resistor (56 @ 5W). I just left that value open for your calculations depending on what you have.

The rest of the regulator is straight out of the National Applications sheet. The sheet calls for tantalum input/output caps on the 317. I used the special HF electrolytics for SMPS use with no ill effects. The applications sheet also mentions this needs for stability, a constant 30mA current drain. I tried without, and it does need it. The 2SD414 (or any medium voltage (100V) NPN with a dissipation of 5 watts will do) is referenced to the -16V rail and guarantees a nice 30mA draw from 0.6V to the output's maximum of 56V. It just needs a 5W heatsink.

The pass transistors heat dissipation can be calculated by the Vdiff*maximum expexted I draw. I could have used one pass transistor, but already had the two mounted from earlier experiments where they had an 80W total dissipation.

The 3A 1N54xx (did I mis-label them? Are they 58xx? meh) need to be there. As the voltage range switches, we're looking at some difference (up to 8V) being dumped through the caps. 1N4007's blow up.

The range selector, relays and supply voltages are such that there is no more than 24V across the regulator on the high range and about 16 on the rest. Referencing the regulator to a negative voltage on the low range allows the output to go as low as 0.6V, perfect for those weired 0.7V filaments and 0.8V filament Russian VFD's.

The meter resistors on the voltage range switch are fine for any 1mA movement for the output voltages expected. But, there's a twist on mine that I *wouldn't expect anyone else* to do, and that's the "Low Scale Heater Resolution" nonsense. The meter I used for this is very tiny. Yeah, I have bigger ones, but (stubborn Dutchman mode) I liked this one.  On the low scale and with this switch on (use the other position for absolutely everything else), it makes the meter read 6.3V full scale and the heater voltage adjust only go as high as 6.3V. I did this because it was too touchy on the low, low voltages. It would be bad indeed to be testing a friends expensive something-or-other with 2.5V filament and blow it because someone across the hall sneezed.

I custom made a meter faceplate for this and has the points marked for all common filament voltages.

The current shunt for the meter will be different for anyone else's though. The meter I used was from a 30's vintage VOM and had the internal resistance calibrated in such a way, common 10% resistors could be used to make the VOM (one of the reasons I liked *this* meter). So, don't expect these everyday 5% values to work for your meter, unless you're lucky.

I scale and CCS... we've covered this before and is the same. But the meter scale for this is worth mentioning - because of the predictability of plate current, rather than making "50%" the pass mark, I've made 80%+ the pass mark, 60-70% a questionable and below 60% a fail. Choose the positions well, small hi-mu tube, little current. At 1mA, it's safe to test tubes with a 90V maximum plate voltage, because the tube draw will pull it down. Higher settings will dump twice that on it and the poor tube unable to pass that much current to pull the voltage down will make the SS gods happy.

Bias control. I've given the tester two bias ranges, 0 to -15V and 0 to -100V for testing high/medium mu and low mu tubes respectively. In the normal position, the gid will be at 0V. Great for testing emission/life/merit, whatever ya wanna call it. Now, we can deduce from curves (or known good tube) at what voltage it should cutoff at, for a given plate current. Just dial this up on the bias and shift the grid. Unless it nosedives below 10%, the grid fails. Because it is operated in a linear mode, I've made "tick marks" on the meter to be used as a way to match tubes at different points. We know better, but it helps to be able to say "ZOMG! MATCHED PAIR L@@K!!!!" and be able to back it up with numbers.

The short test is borrowed from plenty of other tube testers as it's accurate and elegantly simple. A working tube of anykind will have a diode effect. The neon bulb is fed through a cap which acts as a dropping resistor (with some help from a 6.8K resistor because darn it, I just ran out of 0.08679376945 uF caps yesterday) and goes straight to the plate (or other element being tested). If the tube is good, you'll only see a little flash as the cap charges. If it's shorted, the neon lights continuously.

Socket schema isn't here. Paralleled pins to banana jacks are boring. The ones I stuffed into this are, 4-pin (2A3, etc.), 5-pin (807), 6-pin (eye tubes), 7-pin transmitting (829B, 6C33C), 7-pin minature, locktal, octal, 9-pin minature, 9-pin magnoval and 12-pin compactron.

Here's a trick... Use 10 banana jacks. Pins 1 and 12 on a compactron are always heater. Tie them straight to heater and ground. Tie pin 11 to banana jack pin 1. Pins 2-10 are as is, pin 11 = jack 1 

Another builder put up his font panel, I can see there are B9A and Octal bases and couple others possible.

I have also been advised to look at http://www.vintage-radio.net/forum/showthread.php?t=48853

Thursday, 24 November 2011

ESR Meter

The fault diagnosis on the HRO has lead us to belive it might be a failed detector valve and I do not have a spare 6SQ7 or one of the capacitors has gone... so building an ESR meter.

Measuring a capacitor’s ESR (Equivalent Series Resistance) is a great way to assess the condition of a capacitor, vintage or not, particularly electrolytic capacitors .

The design isn't mine, it is based on a series of op amps (TL082, I'll use TL072) that feed a reading into a 100uA meter... (I bought a few 50, 100 and 500uA off ebay a while back) and everything was from the junk box and was cribbed from a old radio magazine. It also has an audible alarm too. I had to substitute a couple components, homefully they will not be too critial but I can replace them if needed.

Not boxed up yet and just built on a off cut of vero board.

I used sockets for the TL072 but did not have any 8pin sockets so used 14 pin sockets instead.

I'll post some more photos of it and maybe an MP4 video of it working.

BTW you can use an ESR meter for more than just measuring electrolytic capacitors see here for more info

After I had already almost finished building I also found this page on the web.

Like that author I didn't want to go and buy an expensive meter when I could build one for pennies and have fun and learn something new in the process.

HRO-5 and Russian Pencil Valves

Hoping to fix my HRO today.... Clive M5CHH is coming over with his and will do a side by side comparison and fault finding to see what might be wrong.

In the meantime I am also looking to build an RX, TX or TRX for other ham band certainly 80m based on the 1b24b or 1sh24b tubes (aka Sputnik) and I am reviewing a few options. There are some great designs out there already  but I'd advise you start maybe here http://www.techtir.ie/blogs/watty/miniature_valves_2 and http://www.oldradioclub.ru/radio_book/book/berg/berg.html for technical details of the valves. I especially like these.


http://www.hi-ho.ne.jp/ux-45/russian.html If you use Google chrome is can do a Japanese to English translation... bit off but readable.



Wednesday, 23 November 2011

DL4YHF Frequency Counter by VU3SUA Sunil Lakhani

I bought a couple (3) kits from Sunil http://cqbitx.blogspot.com/p/buy-digital-dail-kit-05.html and the package arrived today.

It has been sent over in this amazing cloth and wax sealed package.

Opening it was like that kids game of pass the parcel as there were multiple layers before one arrived at the components.

I'll build these up soon.

http://www.qsl.net/dl4yhf/freq_counter/freq_counter.html is the originating site you need to view.

I might attempt this mod

Monday, 21 November 2011

My HRO-5

Was asked to post some images of the insides...

Sunday, 20 November 2011

GQRP Valve Day 2011 (20th November)

The line up this year... HRO RX,  Homebrew 'Scounger' 6V6 TX with crystals and components from all over. My 'new' valve rig is a Codar AT5 which is 80m and 160m CW and AM. antennas are a G5RV (very soggy and will not tune too much condensation in air) and a 6BTV vertical.

Here I'm setting it up the Codar AT5 after cleaning up the inside a little. The meter is duff so I was hoping to swap in a new 100mA meter but although hole and mount screws match the meter is too big... rats so it is sitting by the rig. I get the dip on the meter on the right for now.

I put a plea into GQRP list to see if anyone might have had one of these meters in the junk box and seems I'm lucky so hopefully will not be operating this way too long.

This is the other operating bench, FT897, MFJ993 tuner (top left almost out of picture), I use a Winkey interface with the valve TX and Wintest s/w on the laptop. PSU is a Sharman Multicom PS-SPS250A (switch mode supply and no probelms with RFI) and a Palstar PS-04 that runs all the 12V and 5V (I added 5V output to the read) gadgets on the bench.

I just added a run of CAT5e (buried 18" below ground) to the shack and do not use a wifi connection anymore so the shack now has a reliable internet connection and the common mode chokes (FT240-61 torroids) on at each end seem to have stopped any RF causing issues.

Thursday, 17 November 2011


Selling a MFJ-269 unit from the shack as I have a surplus unit.

I have run though the calibration process here http://www.mfjenterprises.com/pdffiles/MFJ-269_Calibration.pdf

I will post some photos of the unit here if asked.

Thursday, 10 November 2011

K1 Build

This time it is for me and it will be a keeper.

It is a four band model and it also has the nb filter.

Sunday, 6 November 2011

Workbench variable voltage/current limited supply

I just had a some fun with a circuit that was drawing more current than needed and an electrolytic kept popping so after a rummage in the junk box I thought I'd home brew a variable voltage/current limited supply from a salvaged laptop power supply. It worked and was built Manhatten style, anyway I fixed the problem a bridged joint, on the circuit I was looking at. After use I thought I better put this into something more long term as I am sure I will find use for this and I have a nice salvaged instrument case that it will go into. I had not used the more usual transformer and bridge rectifier but a switch mode supply so I have added a common mode choke on the mains input and the DC output from the laptop power supply into the circuit, which is simplicity itself and comes directly from the LM317 data sheet. I use two LM317 to first limit the current and then adjust the voltage.

Looking at the supply with an oscilloscope (must capture a few images and add them) and after a bit of playing with junk box components I added a 3300uF 63V capacitor to the input and a 2200uF 25V capacitor to the output. I might also add a 250K (ish) resistor across both so that when disconnected from mains the input and output capacitors are discharged. I have several 1000uF 100V capacitors I might add later.

The output is via a pair of combined 4mm sockets and binding posts, I will also add a pair of Anderson Power Pole Connections.

An earth connection has been added that utilises the workbench earth and the circuit ground is also connected to. CARE!!! this might not be recommended for any to copy but I KNOW I have a very good mains earth from the workshop supply at the point it enters the workshop and a separate 4mm earth cable is used about the workshop in addition to the 2.5mm ring wiring.

The input 19.5V 4.22A was selected basically as it was available but the important bit for any such supply is that it should be rated at 1.5 times the output and this would allow this supply to provide 3amps. I cannot remember exactly where I heard this but I have not included a 3 amp option and the supply will limit to 1.5 amps, which is also the limit of the LM317 I have used. I could add a pass transistor and obtain a higher current rating.

I will add the circuit but a quick look at the LM317 data sheets (google for LM317 data sheet) will show the options available.

Setting the current limit:
The current limits are set by connecting the ADJ and the OUT of the first LM317 through a 12 way ceramic rotary switch each position of which contains a low value wire wound resistor selected from a recent rally '50p lucky bag', I could have used 1/2W and 1W carbon resistors too. I also purchased a set from JABDOG. The current limits I have set are 25mA, 50mA, 62.5mA, 100 mA, 166mA, 250mA, 460mA (odd resistor value), 500mA, 1.2A and 1.5A the output current limit is directly related to the formula  I = 1.25/R where R is the value of the resistor in ohms. The output is taken into the voltage stage from the ADJ port with the resistor connected through the switch as described connected between ADJ and OUT.

Note that the voltage at this stage is the supply voltage minus the 1.25V drop across the LM317 this LM317 never seems to get hot.

I tested the current settings by feeding this output into a 12V halogen bulb that will run at 50W so is rated well above the power supply with a current meter in circuit.

Voltage Setting:
The variable voltage is set by the second LM317 by adjusting the resistance R1 that is connected from the ADJ port of the LM17 to the ground so that Vout = 1.25 * (R2/R1) where R2 is a fixed 270 ohm 3W wire wound resistor connected between ADJ and the output port of the LM317. The voltage can be varied between 1.2V and 17.3V.

I allowed the supply to feed the 12V halogen bulb at 500mA and left it running for about 4 hours and then remeasured both the voltage and current levels and saw no major changes. At 12V 500mA the LM317 will need to be able to dissipate the heat so I used TO220 version and bolted them to the front panel. The lower the output voltage the more heat is dissipated.

I have not added a meter to measure the current output as the limit is set by switch, the output voltage is another matter and I have employed a 3" chinese analogue meter that looks a bit retro (I might remake the scale).