Project McVan Minilab 604 build

[viorel]

I need a signal generator for use in my hobby shop and looking around and trying a few things I have come to realise the BWD Minilab (McVan) 604 would perfectly satisfy my needs (I need something to generate both 455KHz and 10.7Mhz to allow for radio IF alignment).

So I tried to find one of these units s/h but no luck.

Looking around some more I found the factory manual and it seems it's not that difficult a build so I decided to try and build one (at least the signal generator, amplifier plus counter and display section). The manual I found comes from here:

https://www.kevinchant.com/uploads/7/1/0/8/7108231/minilab_604_v2_maintenance_manual.pdf

Thank you very much to the gentleman who put it up for the rest of us.

Now, the manual is quite comprehensive but it does leave some questions unanswered (at least for my level of understanding - I am not a qualified electronics engineer).

The questions the manual has left are about connecting all the separate circuits in the signal generator section (if you check the relevant schematic you will find a few separate schematics, some are clear where they should connect, some not so much).

If you have a unit and could help with some info or pictures, it would be very much appreciated, thank you.

If you are an electronics engineer and could guide me, it would be very much appreciated, thank you.

See picture attached for schematic:



Another set of questions relates to finding modern equivalents for the chips/semiconductors used in the original design. Most of these are obsolete. You can still find them, but they are most likely cheap clones and I am not sure how well they will perform so I would prefer to use modern equivalents from reputable manufacturers/suppliers.

I should add, I ma looking for direct replacements so I do not have to modify the schematic (because I wouldn't know how).

So here they are:

LF441 - I found LF444 - can I use that?

LM353 - is TL072 a direct replacement?

LF351 - ?

MC1445 - ?

LM6361 - ?

[orzel]

Can't help much, but i also noticed this ... weird/fun/useful gear. And i also noted schematics were available. Did you get anywhere... ?

[coromonadalix]

generator based on MAX038,   good luck finding them,  production ended in 2001 i think

unless you take chances on fleabay and other  #$##$@%  supplier

when you check all their logo or printings you see some discrepancies

[moffy]

The MAX038 is going to be difficult to find from a reputable source, it unfortunately didn't last that long. If you just need a signal generator then there are plenty available e.g.:
https://www.ebay.com.au/itm/314253349196?hash=item492af5914c:g:NccAAOSwnNVjiBIi&amdata=enc%3AAQAIAAAA8MjjZS70n7ZPbUJnzVMDt3wMa3BxO7%2F5%2FOBOkwj%2FLFl2mYEB9hr33qQVBWgAI8bYCdFpfPSEFlRntVRT5abj8S3N%2Bg5d88jQKbZ3LAbbOjUkHiRElSXMteAIWGqcRO4gC9eL3yAdjE%2BMtd5ElEJNN2Ae%2B1bU3zKA6rU8aLNSjYPTGmSEFhESQG%2F8jYxeM9S%2F%2FSPRsJWvmT2v8izviQa0roJWxjbKajWjQTLndDcGhQRugktE4PocctoRxg2acMoSk8odWBOedCFRa1xEX9RMWs16EBeX9vk9WKMT6Zkh81j8rcncrt%2FF9R99QHafd4KO8Q%3D%3D%7Ctkp%3ABk9SR-C2r6idYw

I can't speak for that model but it is an example of what is available.

[orzel]

If you just need a signal generator

That's not the point. The gear we're talking about is an all-in-one with lot of different features, signal generator is only one of them.
And it's more about "this thing is fun, can we reproduce it" than "Searching for the ultimate xxx gear". There are plenty of other threads on this forum for this 
(and i would not recommend the feeltech)

[moffy]

If you just need a signal generator

That's not the point. The gear we're talking about is an all-in-one with lot of different features, signal generator is only one of them.
And it's more about "this thing is fun, can we reproduce it" than "Searching for the ultimate xxx gear". There are plenty of other threads on this forum for this 
(and i would not recommend the feeltech)

Just addressing the OPs statement: "I need a signal generator for use in my hobby shop...".

[orzel]

Just addressing the OPs statement: "I need a signal generator for use in my hobby shop...".

Oh, you right. sorry.
I hope he's gotten one since then though !

[viorel]

Hi everyone,

Thank you for your input.

I have managed to find one in the end and I went through it and serviced it

It works now very nicely and I am more than happy with it.

I have managed to get all the ICs I was asking about. There was nothing wrong with any of its own, but I wanted to make sure I had spares. They are all original, I found them in Japan mainly. I have a contact there who very kindly helps me with obsolete stuff. For the time being, their are all safely stored.

There was only one problem that I could find, one tantalum cap had exploded. I replaced all tantalums with higher spec voltage new ones, I replaced all the electrolytics with beefier Nichicon/Chemicon caps and one low leakage cap (there's only one) with a modern Nichicon.

Everything else was well in spec so I left it alone.

I cleaned some dodgy switches and pots and that's it for the electronic innards.

I have also upgraded all the banana sockets (they were tarnished and looked a bit on the cheap side) to high grade machined gold plated instrument spec Staubli sockets and similar BNC connectors and it's now very happily chooching along. What a nice little unit.

It's very nicely built and laid out, the outer case looks a bit like a kit item but inside it is all top notch. It has a separate chassis of angle steel all zinc plated and shiny, nice high quality fasteners and so on. Very sturdy with cross beams and brackets screwed into each other with proper M3 and M4 bolts, nuts and shakeproof washers. The outer shell is just light gauge sheet metal and it wraps around all the way. The ends overlap at the bottom a bit where the join is screwed together. I have modified mine by cutting a section at the bottom almost the entire width between two screw holes and replaced the section I took out with a slotted section off an old amplifier to allow for better air circulation (it did not have any in the bottom) and added feet a tad higher than original. This new section overlaps both end sides of the old shell and it is screwed on using the same screw holes that were there (I don't like drilling holes in stuff). Looks very factory and has much better cooling. Not sure that is needs it, but now it is very easy to remove the bottom section I replaced and get full access to the underside of the main PCB.

PCBs are very beautiful and all soldering looks like a proper instrument should. The factory and designers did a great job in my opinion. No idea what these cost new but they do not look cheap at all inside. Very easy to service too. I strongly recommend it for hobby grade use.

[EEVblog]

generator based on MAX038,   good luck finding them,  production ended in 2001 i think

I published and sold a 20MHz MAX038 function generator kit, lat 90's I think. Great chip.

[EEVblog]

Wow, you can get MAX038 function gen kits on Aliexpress.
https://www.aliexpress.com/item/1005005137744198.html
Does someone still make clone? because the original is crazy expensive.
https://octopart.com/search?q=max038&currency=USD&specs=0

[grenert]

I published and sold a 20MHz MAX038 function generator kit, lat 90's I think. Great chip.

Is a 20 MHz circuit something that can be built on veroboard or is a proper PCB required?

[ledtester]

Wow, you can get MAX038 function gen kits on Aliexpress.
https://www.aliexpress.com/item/1005005137744198.html
Does someone still make clone? because the original is crazy expensive.
https://octopart.com/search?q=max038&currency=USD&specs=0

It would be nice to know how well the Aliexpress offerings perform from someone who has had experience with the originals.