Intermission

The recent lack of progress has been fuelled by two parallel causes. Mr S, collegue and partner in crime, had to make a trip to Europe's mountains over a week. Also, central components for the Detectron computer, like the motherboard, are still being shipped (although probably by truck). While waiting, the current workspace was put to the test in restoring an old Sansui Stereo (1974), which is described in this post.

Although much of the hardware is still in transit, the tools, multimeters, and the phidget USB I/O cards have arrived. To complement the sterile, efficiency seeking table, a 60s string shelf has been filled with orchids, porcelain och cooking books. 

The Sansui Stereo receiver 771 was bought from ReHIFI a few years ago. It has a really warm and cozy sound that shines especially when playing classic and jazz. However, it did have problems with dropping one of the speakers every now and then, and making weird noises when turning the volume or equalizer knobs. The amateur diagnosis is that the potentiometers and inputs/outputs probably have become dirty during the last 40 years, and maybe a simple cleaning could fix things.

It turned out that one of the hardest parts in the restoration was to actually break into the stereo. After removing the wooden case with four simple screws, it took several hours to figure out that the front panel was actually attached behind the knobs, apart from the two screws on the top. Apparently the principle of single purpose does not apply to vintage stereos, and combining key structural support with sensitive input is not a problem. Behind the front panel could be seen the I/O circuit card that handled the knobs and buttons, along with the sought potentiometers. Unfortunately there was a lack of pictures taken of the inner workings, likely due to the excitement involved at this point combined with diverse family members requiring attention.

The insides of the stereo was first dusted using a vacuum cleaner and a paint brush (method taken from this post). There was surprisingly a lot of dust, although the domestic surroundings that are the stereos natural habitat are stringently clean... ahum. After this the potentiometers were cleaned with pressurized air, followed by a round of potentiometer cleaning spray. All inputs and outputs were similarly treated but using the regular contact cleaning spray.

Typically old stereos need a replacement of all old paper capacitors, since these loose their function with age. However, since the stereo has a very nice sound as it, it seems very likely that this was done at ReHIFI before the purchase. The capacitors also look newer that the rest of the electronics. Also take note of the highly analog (string-driven) radio tuner dial.

 

Before reassembly, a sort of successful attempt was made at replacing the old power cord with a new, grounded one. This did work out, but involved some very poor soldering, which is shown in a figure below to encourage any other enthusiasts. There was also an effort to replace the backlights for the tuner display into LEDs, but it turned out that they were operating on AC (multimeters are great!), which made the needed circuit construction and soldering a bit too scary compared to the small gains.

 

In conclusion, the issues experienced before restoration seem to have pretty much vanished. The stereo, now coupled to a Bluetooth receiver, played very diverse music flawlessly for four hours yesterday. The only thing that's still a nuisance is that one of the three pairs of speaker outputs still drops a speaker occasionally, but every old device needs it's own personality.

The Receiver case mod

After mentally streching the Detectron in all kinds of directions, it has been decided to convert the receiver part into a small computer. This makes it a pretty major case mod, although it's more like a case genesis for a proper nut case. Everything in the case has to cleared out and built anew. In this post the design and components of this computer will be described.

It turns out that the size of the case is quite limiting for fitting in a decent general purpose computer. The mini-ITX form factor is needed for the motherboard, sporting only 170x170 mm, as well as a smaller power supply unit. Apart from the concern of physically fitting all the components inside the case, heat could very well be a problem in such a confined space. From this under-researched gut feeling it was decided that a i5-4570S processor could be suitable, were the S means lower power consumption - meaning less heat output. To complement this, a high-end but low profile Noctua CPU fan was chosen, along with a smaller Noctua case fan. Solid state drives make little heat and take little space, so this was an easy choice.

• ASUS H81I-Plus LGA1150 Socket, LGA1150 Socket Mini ITX  
• Intel Core i5 4570S / 2.9 GHz processor 
• Samsung 840 EVO MZ-7TE250 250GB 2.5" Serial ATA-600
• FSP 1U 220W ATX12V
• Kingston ValueRAM DIMM 240-pin 8GB 1600MHz CL11
• Noctua NH-L9i
• Noctua NF-A4x10 FLX

So how does it all fit together? Let me present a little mockup...

The mini-ITX motherboard and small power supply unit just about fit in side by side, it the bottom of the case. The Detectron should be standing when operating, and all connections will come out of the right side of the box. Now because the case inner height is only 62 mm, it is going to be very interesting to squeze in the SSD and other things in a second layer. We also need some space for air to flow trough for cooling.

Now there was just a mention of other things, and there is one thing in the sketchup that hasn't been presented. Yes, what is meant is the circuit board sitting on top of the power supply unit. This is a USB I/O board, from the possibly (haven't tried yet) excellent company phidgets. From the Detectron introduction post we see that the old knobs sported very large electronics on the backside to create their functionality. Now we cannot keep those while filling the case with a whole computer, and also we have no idea of how they work, but we still want them to be functional! Therefore, a phidgets I/O board, a phidgets analog output board, and some phidgets switches and sensors will be used instead to retain functional knobs and buttons. What exactly they will be used for is another topic, suggestions would be welcome!

The Detectron

While cleaning out Ks mothers garage, we found some pretty sweet old equipment from Ks dads time working in the Swedish telephone infrastructure. To Ks dismay, the Detectron was for me almost irresistible with it's worn patina over the fonts and style of a Fender amp. In this post, this device is presented in all it's battered glory.
The outside of device is yellow, and in this case orange in places where someone was a bit careless with a spray can. The Detectron is actually a device for tracing cables underground without digging to much, and can be split into two parts: one transmitter and one receiver. 

 

The transmitter (right) and receiver (left) are completely detached once opened. 

The transmitter features some controls: 1) a knob with the 3 options conductive, inductive or battery control, 2) flick-switch between continuous or pulsating signal, 3) connectors for direct coupling to a cable, and 4) a to/from switch.

The received on the other hand has a current-gauge, a low/mid/high amplification knob, and a amplification knob.

The inside of the Detectron is very sparse, compared to modern day electronics. The logic is contained in one hand-soldered circuit board (apparently this is likely made by photo-resistant etching - thanks Jonas!), while all controls sport quite large backsides. The battery is covered in red paper. There is also a speaker and some electronics attached to the antenna, which is the metal rim connecting the transmitter and receiver when packed up.

What will the Detectron be used for, is there a hidden need to treasure hunt cables? No. It will be converted into something useful, and for this reason the inner size of the case have been measured to about 277 x 213 x 62 mm.