HP 8640B – repair update

I can’t help myself, I find I need to further improve this signal generator with the replacement of a failed pass transistor socket so I found some new replacements at RS components. The items I ended up using is a Keystone item KEYSTONE  4602  TRANSISTOR SOCKET, 3 POSITION, THROUGH HOLE from Element 14, order code 1231819.

The Keystone part is not exactly the same as the original and I found it tricky to solder on the new one so that it is the same “height” above the PCB as the others but I got it close enough. The problems though is the legs of the mounting socket which are also the connectors to the circuit protrude through the PCB and is at a 90 degree angle to the power supply board behind (which the Pass transistor feeds). As it turns out one of the legs of the new pass transistor socket was sticking through just enough to come into contact with the heat sink of one of the transistors on the power supply board, the end result when I applied power was to blow one of the 3/4 amp 120V fuses and so I lost the +20V rail. Oh well, I fixed something and then I broke something – a familiar story.

Back onto Element14 and had a search around for some fuses to match, ended up finding one and it was received yesterday – LITTELFUSE 273.750 FUSE, PCB, 750mA, 125V, VERY FAST ACTING, order code 1200264. When trying to replace the old one I learned that in fact the original fuse is easily removable because it is pushed into 2 little sockets soldered to the PCB, one for each leg of the fuse – pretty neat! The issue though is the new fuse didn’t have the required leg spacing so I just soldered it to the back of the board where the fuse sockets are soldered so no harm done to socket if I ever want to replace with an original again.

Lastly, I had to replace the Rifa mains power capacitor – it sitting there in its sorry blown state – having let go the smoke years ago was doing my head in. Bought a Safety Capacitor, 2200 pF, Y2, B32021 Series, 300 V, order code 1609515 again from Element 14. Installation of that went fine, no new problems caused during the process.

HP 8640B signal generator repair

As sold, not working. An oldy but a goody.

I seem to have gone down a rabbit hole that a few others I read about have travelled. It goes something like this. You have the remote need for some esoteric test equipment to work on radios and stuff and you are overcome by the shear beauty and horrifying complexity of HP’s equipment from the 70’s, 80’s and 90’s.

Truth be known, I had a frequency counter and a signal generator already but they were not what I wanted and so, during a car boot sale in August I purchased a HP 5328B for an amazingly reasonable amount given what they cost when new (this too seems to be a point many in my boat make). I couldn’t wait to get home and take a look inside. It has the crystal oscillator oven and seemed to me to be a lot larger and make a lot more noise than would be expected to perform this task but it is gorgeous inside with it’s 1970’s vintage gold trace PCB’s and red 7 segment display. This immediately led me to start searching for more HP equipment, the next being a signal generator.

I was lucky to find one for sale on eBay, not working, from a chap here in Perth and so put and offer in for this HP 8640B and picked it up. Seem these units are used as a bit of a standard when it comes to quality of signals produced.

After getting it home and plugging it in, sure enough it did not work – the fan came on but there was nothing else working, no display, no needle movement – nothing.


First things first I ripped the top and bottom covers off and took a look at the power supply boards, all but 1 of the red LED’s were on, the one off was (from memory) the +5.2V rail. I noticed that the 0.022uF “Rifa” capacitor across the 240V in line had at some stage blown up and let out the magic smoke – this seems to be it’s normal mode of operation at this age and so I noted I should change that at some point but it isn’t going to stop the thing from running.

Pulling the A12 rectifier assembly I tested the multitude of diodes being used in the rectifiers. All diodes seemed to test fine so that wasn’t the problem. I removed the 3 voltage rail cards and re seated them, and I also removed the 4 power supply pass transistors and re seated those as well. Switching on after this finds all voltages are now present and the front numerical displays started working, however, despite my knob twiddling it only had a fixed range of frequencies, ie, changing the range selector had no effect, also, the FM modulation didn’t seem to work and the was no power output displaying on the needle.

One of the many times I had this on the bench

Later, a bit more fiddling with pass transistors finds one of the contacts on the power supply board that connects to one of the legs of a pass transistor had failed (broken) so I I’ll need to get a new connection for that at some stage as it is flaky.

Power supply pass transistors


After a bit of reading I found that a common problem now days is the little contacts that rotate when you move the range switch, deviation and output level are getting to the age where the plastic welding holding them to the plastic switch disc is starting to fail. Sure enough, mine had the same problem and so it was time to pull these out and undertake a repair.

The first problem I encountered was the Allen key grub screws holding the knobs on these controls to the shafts on the switch mechanism. I loosened all but one of the grub screws (it’s always just one isn’t it) in the knobs, the last one ended up stripping internally so the Allen key just spun. A vain attempt to remedy the situation by gluing the Allen key in there with super glue and Devcon failed as expected. These grub screws are hardened of course so no normal drill can drill them out – I had to order a special 1.5mm solid carbide drill bit from RS Components to have any chance of drilling it out – this tiny bloody grub screw put a stop to the project for 2 weeks while I waited for the drill bit to arrive. After arrival of the drill bit I was able to drill out the grub screw – I’m sure this must happen all the time as the grub screws are very small – why they didn’t go larger I have no idea – seems plenty of room to go up a size or 2 on the range switch knob.

Range and Deviation selectors in the instrument

After finally getting the combined Range and Deviation switch mechanism out I found I was missing 5 of these little contact fingers across the 3 separate rotating plastic discs which had come loose and fallen off over the years into the bowels of the machine and despite my searching and shaking of the instrument, I could only find 2 rattling around in there so I had to make 3 new ones.

Oh dear – none left on this at all!

I ended up visiting my local electronics store and bought a range of components that I hoped could have internals that would work as replacement contacts, this range of components included an edge connector block which, after pulling apart had an almost endless supply of contacts if you undertook some modifications (see below). These replacements are made of a thicker gauge metal which may be a problem and one must remember to remove any sharp edges that may exist on the contact fingers (I used a very fine Arkansas sharpening stone) so as to not damage to PCB that it contacts with.

After using a 2 pack epoxy to glue the old fingers on again and also the 3 new made fingers I had the range function working again and the modulation selector seemed to work as well.


This too seems to be a common fault in these machines. Apparently the plastic used was called Delron and that has a tendency to shrink over the years causing stress cracks as the hub the gears are cast on is brass which will not shrink and so something has to give.

One of the bevel gears was badly cracked so I broke it completely and then glued it back again using epoxy. After drying one of the teeth just wasn’t quit lining up well enough to mesh properly and was jamming things up; a little bit of a file on the offending tooth to widen the gap was just enough to gain clearance needed and it all rotates as well as can be expected.

As a side note, remade solid brass gears are now available online which may be on the Christmas list this year.

Range and deviation assembly detail


Even after getting the range switch working the gauge showing output power was not registering anything (it worked when selecting AM or FM modulation % but not output level voltage). I tested the AGC board and its didn’t seem to be giving me the correct readings. A bit if hunting around and tracing resulted in me pulling out the output power selector/attenuator assembly which had another analogue switch rotor with the same little contact fingers on it. In place inspection the contacts looked to be there but on removal I see that 3 of them were broken and wouldn’t have been making good contact – if at all. Seems these contacts feedback into the AGC which in turn feeds to the power meter and so its an important part of the output circuit.

Gluing on these contacts and reassembly it all seems to work again, needle moves with changes in the output power vernier, annunciator lights work as expected. YOU RIPPER!!

Working in all it’s glory. Yes I know the 8640B also has a counter built in but where is the fun in that.


This instrument is the first one I worked on and I learnt a lot. Just getting my head around the HP Service manual was a steep learning curve but I’m happy to have a fully functional signal generator. I have now sold my old signal generator and frequency counter and have these HP machines proudly in my office/lab. I plan to get a few more HP instruments, would be good to get a Spectrum Analyser so am on the look out for a broken one to try my luck again.

BBOS 10 and WhatsApp late 2018

I’m one of those odd balls that still uses a Blackberry, its a Blackberry Passport Silver Edition and it runs BBOS

From time to time I use WhatsApp, the problem being is WhatsApp stopped supporting BBOS at the end of 2017 so you have to find a work around to get it to work again.  Teh solution involves side loading an APK and installing a helper app called WhatsFixer.

My WhatsApp installation worked till a couple of day ago and then stopped working after warning me everyday fro the last month that I had to upgrade –  the version was too old (from Jan 2018).  I guess the application has a kill switch inbuilt  or something to stop  old versions with bugs being out in the wild for too long.

I had to install a new versions but the newest version (2.18.268) didn’t work properly.  It would install fine and WhatsFixer seemed to run OK (it’s hard to tell what WhatsFixer does).  Strangely with version 2.18.268 & 2.18.266 when you go to send a message to one of your contacts the app would crash after showing a box saying it had stopped working.

An odd work around is to deleted all the voice calls from the WhatsApp call history and then send a message – it will work, but, make another call and then try sending a message and it will crash again.

To get it working again without this “bug” I had to side load WhatsApp 2.18.105.  There may be later versions between 2.18.105 and 2.18.266 that work fine – let me know if anyone else out there has the same problem.

Have you seen the price of Bitcoin

Way back in 2011 I was slagging it off, amazed that it had climbed to USD3.50.  I should have made a substantial investment then but that is the benefit of hindsight.  Now, the price is approaching AUD4000 each!

I bought a few back in 2012 but no where near as many as I should have…..

Bitcoin price 2017

First job on the Lathe

I got hold of a new desk for my study 6 or so months ago and finally got around to assembling it.  My old desk was a cheap and nasty Ikea job and during its disassembly I broke it a little bit which wasn’t a big deal because the new one would take it’s place….I thought. Turns out the little screw cam fittings which the new desk came with and which are the means to hold the thing together were not the right ones so I have been without a desk for a couple of weeks.

Having called a few companies that sell these types of screws it was looking like I was going to have to stump up $40 odd dollars for 100 new one’s, thing is, I only needed 10 and I am a scrooge.

Dad has had an old Hercus lathe for many years and I have always wanted to get my hands dirty using it for a reason other than to just piss about with it – today was the day.  Behold the made parts from modified M7 bolts!!!

Amazing the trouble to go through to make these.

And the Hercus 9″ Lathe they were machines on….

Good old Hercus 9″. Good enough for this odd job and a very handy Australian made piece of kit from the good old days.

New Mythtv setup

Our old combined MythTV front & backend is getting old and the root partition was continually filling up (I know, I could make it larger with GParted but it takes for ever) so I decided to change things over the Christmas holidays.

My new set up consists of the following:-

  1. HDHomerun network TV tuner (dual tuners in a tiny box)
  2. Old broken keyboard laptop as the back end only – tucked away in my study with the rest of the network gear.
  3. Zotac ZBOX ID80 front end running OpenELEC
  4. Applet TV (version 1) front end modified with the installation of a CrystalHD video decoding card running OpenELEC (special build for the CrystalHD ).

HDHomerun tuners are a complete change in the way you think about TV tuners and what can be done now.  Basically the HDHomerun streams the data that it gets from (what ever terrestrial TV channel its currently tuned to) over your network ready for what ever system wants to pick it up.  In my case the Mythtv backend controls which channel the HDHomerun is tuned to and either records direct to hard drive or throws it at a front end as live TV if that’s what you want.

For the back end I decided to run Mythbuntu.  I have been a big Arch Linux user over the last 8 years and currently run LinHES but having downloaded the most up to date release it didn’t seem to work properly on my laptop so I decided not to battle with it and roll over to Mythbuntu.  Mythbuntu seems to have a more active development than LinHES and given its based on Ubuntu’s LTS releases I decided to go with it.  Installation (as with all Linux distros now days) was very simple.  It picked up the HDHomerun without me doing anythting as it has a HDHomerun tool pre-installed, I used this same tool to update its firmware.

OpenELEC is basically Kodi (the new name for XBMC) pre-built on top of a lightweight linux distribution.  You down load it, install it onto a USB drive and plug it into the device you want to install it on, a couple of clicks later and wammo all done!  After installation you point it to the Mythtv back end it needs to use.  This set up lets you have one central machine that schedules recordings and stores the data while you can have several remote front ends sitting under your various TV’s which will talk to the back end and stream the TV recordings or live TV from the back end.

The Zotac box is very capable and will be the main unit we use (upstairs TV).  We use a Bluetooth keyboard with this setup – don’t use the remote control, I find it comes in handy when I need to open up a terminal if something goes funky.  The remote that comes with this ZBOX is a little small and flimsy – wouldn’t cope long with getting used continually by a family I recon.

The Apple TV 1 is a great solution for a front end but as its an 8 year old piece of hardware its really getting towards the end of its useful life.  The addition of the CrystalHD card breathed new life into these machines as a solution for a Media center.  My particular piece of hardware was unused when I bought it 6 months ago so we should be OK for a little while.  Compared to the ZOTAC box the ATV1 has a little bit of lag but its good enough.


HDHomerun findings

The HDHomerun was already in service with my existing Mythtv combined front/backend.  It seems to me there are restrictions on how many devices can connect to it – not sure if that is hardware limited or firmware.  In any event, if I tried to stream a TV show to the new Mythtv front end (which in turn was connected to the new back end which in turn was connected to the HDHomerun) most stations buffered and couldn’t get enough data to display a picture or audio stream.  This was the same  if I tried to play a stream direct from the HDHomerun from within the Mythtv Backend using VLC (Mythbuntu backend has a GUI installed with a handful of tools/applications, one of which is VLC.  I could watch the bandwidth value coming from the HDHomerun (using the HDHomerun toll in the backend) when I tried to stream in this configuration.  Some stations were up around 7 – 8 MBps but the stream would not work, some were much lower (less than 1MBps) and the stream was obviously broken.  Interestingly, ABC News24 would work with a 12-13 MBps stream rate – I’m not sure why but there you go.

This was a bit of a worry for me so I left it for a day but then recalled I read something about there being a restriction on the number of devices connected to the HDHomerun.  With this in mind I shut down the old combined front/backend and restarted the new backend.  This seemed to “fix” the issue.   Streams were now working fine in VLC and also to the front ends.  So, if you are testing a new PVR installation using HDHomerun as the TVtuner and that HDHomerun is already in service on another system then this is going to cause you problems – shut the old system down, restart the new test system and you *should* be OK but YMMV.


OpenELEC findings

OpenELEC is Kodi, the interface to Mythtv being an Add-On so really, the Mythtv solution is secondary in OpenELEC so its not as good as a true Mythtv frontend installation.  That’s not to say OpenELEC is a good solution, its very polished with a gorgeous UI and long list of Add-Ons for all sorts of media related things (Movie DB and TV DB scrapers, fan art etc) but there are a couple of issues here still to iron out.

The recording  scheduling in the Mythtv Add-On is not as advanced as full blown mythtv front end is.  Perhaps I’m wrong but there is no where I can go in the scheduling where I can select a TV program then schedule a recording of that show when ever it is on that particular channel or once per day or once a week like you can in a mythtv front end.  You can record a TV program if you are watching it and do some very basic scheduling based on channel and time but that is about it.  To get around this I have to do the scheduling using Mythweb – kind of a cludgey work around I think but let me know in comments if there is something I have missed in the Mythtv Add-On.


Email migration to Fastmail

During September I completed the migration of email from being self hosted and maintained email server to that of Fastmail.

I first heard of Fastmail around 10 years ago from a friend that I used to live with in the UK, he was in IT so I assumed Fastmail was a pretty decent offering for him to recommend.  Back then Fastmail also provided access to your emails using the IMAP protocol which to me, back then, was an amazing solution giving you the ability to have several devices with your email on and all kept “in sync” as the email wasn’t located locally, it stayed on the Fastmail servers.   This is a pretty common thing now days but 10 years ago POP was the most common.

Around 4 years ago I started using Fastmail as a back up mail server for the times when my own mail server went off line.

Fastmail have a migration tool which is very useful for moving all your existing emails at your old email host.

So far its been practically painless.  The only thing I have noticed is that the dates shown on some emails when I view through Fastmail’s webmail interface have been changed so that I have a block of email from some random date in 2012 and in 2013.  Not sure why this happened but a few support tickets later and Fastmail have fixed everything now so all dated correct.

So, if you are thinking about hosting your email with Fastmail I recommend you do.  Its all they do and they do it well.

Cape to Cape 2014

A week after the Cape to Cape ended and I am still a little weary, just can’t seem to shake the tired when I wake up in the morning.

It was a busy 4 days with over 220km of off-road riding through the southwest of WA.

Day 1 – Lots of big hills, in fact the first major climb started around 2km after the start.  For the rest of the 40km there were plenty more climbs.  If I am honest I should have pushed a little harder going up the first climb to get further up the field.  Many of the riders wouldn’t try riding up the hills, immediately getting off to push which prevents you from riding yourself as it bunches everyone up and everyone gets off to push.  Beach section was a push fest, very dirty at the end.

The race seeds you on the result of the first day, there after you start in that group you have finished.

Day 2 – Hills, nice views.  One section just after a quarry there were 3 very steep but short rises to climb; I got up them all riding, the rest of the mob around me were walking.  By half way at the water point I had not drunk much so I topped bottles and rode on.

The last 25% was through vineyards including Leeuwin Estate (right in front of the concert bowl – home of the famous Leeuwin Estate Concert and then onward through a bunch of other vineyards after finally finishing at Xanadu Vineyard.

Day3 – Up and down again.  Started with an 8km roll through Margaret River on the roads then into the bush for some medium climbs.  I had someone crash in front of me going down a hill and I landed on top of their bike hurting my knee and loosing my GPS.  After that we went into the pines single track near Margaret River, through several creeks that by the time I came to them were black muddy messes.  The final hill was a ripper but I got up it without walking, the finish was at Colonial Brewery – absolutely filthy.

Day 4 – The longest day (65km) but a mix of single trail, gravel tracks and a bit of tarmac.  A few big hills today but I was feeling OK.  Overtook many on the final 20km.  The last 5 km was single trail at the Dunsborough Golf Club.  By then I was getting tired and could have done without this part but no accidents and a sprint finish with some bloke pushing it down the finish straight.

What I learned

  1. You can never eat to much.  In fact we ate like pigs and were still worried we didn’t have enough calories coming in.
  2. Water is fine but on long events make sure there are electrolytes in there as well (I had a twinge of a cramp on the finish line on day one, there after with electrolytes I was fine)
  3. Camping and racing isn’t as bad as I thought – as long as you have a good camp cot and the other guy you camp with has a fully kitted out camp trailer its not bad at all.  Thanks Chris!

Cape to Cape 2014
Dirty at the end of day 1