https://canadianvintageradio.com/

Radio Restoration, Victoria, BC (2026)

10/25/2026

I decided to check the condition of the electrolytic and some other capacitors in the McIntosh MX110 tuner/preamps today. Before I did this, I had already decided that I would be replacing the tubular electrolytics and the 'tropical fish' and 'mustard' (plastic film) capacitors that had been installed in place of some disc ceramic capacitors in the signal path in unit 'A' (at least one of these replacement was showing signs of distress, ie. cracks in the plastic encapsulation).
The main reason for the (in-circuit) checks using the ZOYI ZT-DQ02 meter was to have an idea of the condition of the installed capacitors, especially the multi-section can electrolytics. Although the latter seemed to be ok, as evidenced by lack of significant hum on the audio, if the units are to be used often, then it may be sensible to replace them with new parts given that they are around 60 years old. If they are to be replaced, there are several options, which I have presented to the owner for discussion and for him to decide on (see below).
In-circuit testing of capacitors is never 'definitive', but I have found the ZOYI to give reasonable results if the test signal level amplitude is kept low and the appropriate test frequency is selected (depending on the position of the capacitor under test in the circuit of course). However, the ZOYI unit cannot measure leakage current at the working voltage of the capacitor, which is an important consideration.
I have received a quote for the six multi-section can electrolytic capacitors (3 for each MX110 unit) from a well-known supplier of repro/bespoke multi-section can capacitors (in the US). Note that the prices quoted are in US$ and do not include shipping, taxes and customs duties.
1) Can capacitor 40-40-20-30uF @ 300-200-350-200V = US$42.50
2) Can capacitor 50-50-50-50uF @ 200V = US$43.95
3) Can capacitor 1000-2000uF @ 15V = US$41.90
Total for six (6) can-capacitors US$256.70
The CDN$ cost using a recent FX rate (1.355 CDN$/US) would be CDN$348, plus shipping, taxes and customs – I would say the total would be over CDN$450 for the two units, so quite a cost outlay (though I have no idea if there would be any sort of additional tariff imposed by the US on top of this given I am in Canada). The cost for one MX110 unit including shipping and taxes would likely be around CDN$260.
For comparison, the costs for ‘generic’ tubular electrolytics from a Canadian supplier I often deal with would be (for 2 units):
1) 2 x 68uF 250V, 2 x 40uF 350V, 2 x 20uF 350V = US$16.38 (one of the 40uF and the 30uF parts are connected in parallel to give 70uF in the original can capacitor, so I would use a single 68uF part in each unit for these instead)
2) 8 x 50uF 250V = US$24.72
3) 2 x 1000uF 50V, 2 x 2200uF 50V = US$16.76
Total (for 2 x MX110) = US$57.86 (CDN$78.4), or CDN$39.20 for one unit. That's quite a difference in cost outlay!
Given this, I think that if these were my units, and I wanted to/needed to replace the capacitors, I would re-stuff the originals if I cared about retaining (mostly) the original under-chassis appearance, or leave the originals in place, disconnect them, and wire the new parts in under the chassis if not.
The decision must be made in consideration of many factors, including available budget, perceived longevity of the replacements, above and below chassis cosmetics, potential resale value, and 'peace of mind', as well as ease of installation.
I will likely be busy with non-radio stuff for the next few days, so this will allow the owner to give this some careful thought. Hopefully, I will have an opportunity to discuss the pros and cons of each approach with him soon.

10/25/2026

Well, what can I say...
Following on from my last post where I noted that I could not test the 6DS4 nuvistor or the 6D10 compactron tubes on my STARK 9-66 as I did not have the correct adapters, the owner of the Hickok 539C that I checked out a while back contacted me to say "One of your friends [him] has a tester for those...", then noting that the Hickock 539C "...is uniquely equipped to test both nuvistor and compactron tubes natively because its front panel includes built-in sockets for these types". Yikes! - and his Hickock 539C is still sitting in my 'shop!! (due for return next month). Hmmm, how fortuitous. Serendipity strikes again!
So, I hauled the Hickock 539C from my storage area and onto the side table and sure enough, it sports those socket types, and the 6DS4 and 6D10 are both listed on the roll - yeah!
I tried testing one of the 6DS4 nuvistors first - I set up the tester appropriately, plugged the tube in and pressed 'P4' - nothing registering on the meter. I knew the tube was not 'dead' as the tuner it was installed in (unit 'B') was working. Close inspection of both the nuvistor pins and the socket revealed some tarnish, and the socket tines looked a little widely-spaced for the nuvistor pins, so I reckoned that the problem was poor contact between the tube and the socket.
I lightly scraped the nuvistor tube pins with an Exacto knife blade and then polished them with a cotton-tipped toothpick dipped in Deoxit D5. I then gently re-set the tines in the nuvistor socket and dropped a little Deoxit D5 into them also.
On re-inserting the tube, the meter now read ok, with this tube having a Gm of over 7500 (a typical Gm value for 'good' 6DS4 is around 4500) - so a good tube. I then tested the nuvistor from unit 'A' and found its Gm was only around 2000, so very weak.
I then tested the 6D10 compactrons from each unit. At first I tested them (in error) using the 'Low Plate Volts' setting (as I had been, correctly, for the nuvistors), resulting in the one from unit 'A' seeming to have one marginal section, and the other two sections testing ok (a typical Gm value for a 'good' section in a 6D10 is 2500), and two sections in the compactron in unit 'B' seeming to be marginal, and one section fairly weak. However, when setting the plate voltage switch to 'Normal', as it should be for this tube type, all sections in both compactrons tested ok, with Gm values ranging between 2700 and 3100 for the one from unit 'A', and between 3100 to 3300 for the one from unit 'B.

10/24/2026

All I have had time to do on the McIntosh MX110 tuner/preamp units is to test the tubes in them both.
I have decided to name them unit 'A' (the one with the chrome plating in good condition that the owner had been using), and unit 'B' (the one with the rusty chrome plating that the owner bought, but had not tried out).
I could not test the nuvistor or compactron tubes as my STARK 9-66 is not fitted with the adapters needed (I plan on checking with friends to see if they can test these tubes).
II found several issues:
Unit 'A':
- four weak tubes (V2,V3,V7,V8) – 2 x 12AT7, 6AB4, 6CS6;
- two 'marginal' tubes (V14,V15) – 2 x 12AX7, and
- two substitute tube types (6EA8 tubes fitted instead of 6U8 tubes, V11,V16). The 6EA8 and 6U8 tubes are both medium-mu triodes/sharp cut-off pentodes, with similar characteristics (the 6EA8 has slightly higher transconductance values) - they both tested ok.
Unit 'B':
- six weak tubes( V3, V7, V9 (eye tube), V13, V14, V15) – 6AB4, 6CS6, 6HU6, 3 x 12AX7, and
- one incorrect tube: a 12AX7 had been installed in place of a 6U8 in the decoder circuit (V11) - no wonder the decoder was not functional (or at least one reason!). The 12AX7 that was fitted in place of the 6U8 tested marginal, though the pinout and characteristics are completely incorrect(!).
I did not test the 6HU6 eye tubes in the STARK tester, noting them as ok or weak depending on brightness only.
I have provided the owner with some options for recapping these units and await his input before I order any parts (I know he wants 'audio grade' capacitors in the signal path).

10/22/2026

No progress on the McIntosh tuners - too busy with non-radio 'stuff' at the moment...
That said, I did managed to head to the Victoria Radio Group meeting last night. Several items of test equipment, a couple of radios and a large tuner for sale - all at reasonable prices, plus some freebies and a show and tell, Good conversation too!

10/21/2026

The Eddystone presentation I made to ARCI is now also posted to the Eddystone User Group website, here:https://eddystoneusergroup.org.uk/wp-content/uploads/2026/10/From-Hairpins-to-Radios-Eddystone.pdf

10/21/2026

Before I started pulling and testing tubes, I decided to take another quick look at the first MX110 unit today.
I thought I would check to see if the 'MPX Stereo' indicator (always off in this unit) was an easy fix, ie. was it simply the indicator bulb that had failed or did something more serious need troubleshooting?
To access this bulb, the metal screening cover over the top section of the tuning mechanism/preamp pre-set level controls has to be removed. The bulb holder is not that easy to access, as its under several lengths of the dial cord, but I found that the bulb could be manipulated out by passing a couple of fingers under the metal bracket that supports the pre-set pots and the dial light dimmer switch, while a couple of fingers from my other hand were passed between the dial cords - maybe not the best bit of engineering by McIntosh...(!)
The 'MPX Stereo' indicator bulb is a an unusual type (at least in vintage radio circles), ie. a #1850, which is a 5v 90mA bayonet part, which I do not have in stock. Rather than risk a #47 (6v 150mA) bulb in its place, as the driver transistor is only rated at 200mA maximum collector current and 0.175W maximum dissipation, I thought I would try an LED dial bulb.
I was given a bunch of these some time ago by a friend - actually a couple of different types (they are popular with pinball machine restorers as, presumably, it saves lots of bulb replacement time and relay contact wear). I checked the current draw of one type and found the current draw to be only around 7mA with a 5vDC supply, so worth a try. I found that this LEDs worked ok (sort of) - there is still some illumination when no signal is being received, but it gets noticeably brighter when a stereo station is being received. I may play around with the circuit later to obtain better contrast, or pinch the bulb out of the other MX110 unit (or maybe even order the correct bulb type!).
While I was looking over this chassis I noticed a few issues I had not notices previously, including:
- a couple of wires running from the phono sockets on the rear apron through a flexible metal tube to the input selector switch (tape head input) had been snipped, and replaced by a couple of unshielded wires just 'hanging in the breeze';
- several of the capacitors that are disc ceramics in the other unit were of a different type in this unit - here, they are 'tropical fish' plastic film ones, one of which had cracks in its body, so should be replaced. Interesting, as they look to be original fitment, but I think they are likely replacements as, as far as I am aware, this type of capacitor was not in general use by US manufacturers;
- a damaged 2.2Mohm resistor located behind the front panel - needs some investigation; and
- the four B+ supply bridge rectifier diodes (each a GE Type '6RS20PH6RGD1' miniature selenium stack) have been replaced, or at least bypassed, with silicon diodes.
I plan on testing all the tubes later today, before starting to trouble shoot the muting circuit and re-do the tape head input wiring in a more satisfactory way.

10/21/2026

I powered-up the other MX110 tuner/preamp last night - slowly, using a Variac. It works, though like the other unit, it has some issues. These include no output when the stereo decoder is switched in (output on mono FM is ok), the stereo light is always on, the volume pot is very noisy, and the dial lights are both dead. The good news is the muting circuit is working ok, as does the tuning eye – its quite dim, but has a better range of movement than the one in the other unit, ie. the display is wide open when no signal is being received, and is just closed with a strong signal.
I am not sure at the moment if the owner wants this unit refurbished (to keep or sell), or whether he wants to keep it as a spare as-is, or as a potential donor/'parts' unit for the other one.

10/20/2026

I had a little time to give the second McIntosh MX110 unit a quick visual inspection yesterday. Apart from the rust showing through the chrome and one missing screw from the trim, it appears to be in reasonable condition, and, from a first look, all-original under the chassis.
I may try powering it up using a Variac later today if I have a chance... but its a 'Wyatt day' and then appointments this afternoon.

10/19/2026

So, a new week, and a new start! I decided to see if the McIntosh MX110 stereo FM tuner/preamp that its owner had been using worked ok. So I connected it up to my QUAD 33/303 amplifier ('radio' input) via an in-line attenuator, and had a listen...
Yes, it does work: its RF section appears to be very sensitive, and the audio sound pretty good too. The EM87 (6HU6) tuning eye works ok and is fairly bright, though its display overlaps on a strong signal and does not fully 'retreat' when no signal is being received. The stereo decoder appears to be working ok, though the stereo indicator is not functioning (could be just a failed bulb?), and the muting control is not functioning correctly (switching it into circuit mutes all signals). All other controls on the preamp section seem to be working ok.
I have it on 'soak test' while I am writing this post - I have noted that the right channel occasionally cuts out/fades. Fiddling with the controls brings it back up (especially the muting switch) - the tuning eye indicates that the RF/IF stages are working ok when this happens, so its likely an issue in the decoder/muting circuit, or audio stages (could just be a dirty/faulty muting switch) - I will be cleaning all the controls and checking out the muting circuit when I recap/service the unit, so hopefully not a significant issue.

10/19/2026

I have been having lots of computer issues over the weekend - Microsoft ‘retired’ their program ‘Publisher’ effective October 14 (it’s part of the Office 365 suite). By ‘retire’, they not only withdrew support, but blocked its use altogether! I have used Publisher to prepare the CVRS newsletter since 2007. Consequently, I could not access any of the past CVRS newsletters (other than pdf copies), or edit the template into new ones.
I knew this was going to happen (Microsoft sent out a warning a year ago), so purchased a ‘perpetual’ license for Office 2021 (last version where they had perpetual licenses available), as Microsoft suggested. I installed it on my laptop after uninstalling Office 365 (as they said to do), however, over a few weeks it ‘morphed’ back into Office 365 as my Microsoft account has my Office 365 license associated with it(!) - the result being I could still not access Publisher after October 14 (see screenshot attached to this post - apparently Publisher is no longer licensed to me).
Microsoft also suggested running Office 2021 on a virtual machine on the computer - what a nightmare: issues with the the virtual machine software, problems installing a copy of Windows onto that, slow response times once installed (even though I am using a fast 'Alienware' laptop!), and, to cap it off, a virus jumped onto my laptop from one of the software download sites, this necessitating a full virus scan that took 12 hours to complete to remove the virus (I had no idea I had 6 million files on this computer!).
After that nightmare, I gave up on that approach, and instead installed it on my older laptop after signing out of my Microsoft account on that machine and setting up a new Microsoft account (with a different email address), then installing Office 2021 on that computer. So far it seems to have worked (fingers crossed). Two days of my life I will not get back…. and not a radio fixed!

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