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Old 28th Mar 2020, 12:51 pm   #1
theredhouseinn
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Default Wavetek model 146

My wavetek 146 has packed up. No o/p from either the main or aux sockets.
All p/s volts are ok.
I have poked around with the scope probe in both sections, but no waveforms can I find.
Does anyone have a cct of this machine?
This is a vintage machine so it can easily be worked on. Discrete components.
In each section there is a block 2" x 2" x 1" high, what are they?
Any info would be appreciated.
john.
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Old 28th Mar 2020, 1:27 pm   #2
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Default Re: Wavetek model 146

Manual here:-

http://manuals.repeater-builder.com/...nstruction.pdf
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Old 28th Mar 2020, 3:03 pm   #3
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Default Re: Wavetek model 146

Working on very old and hazy memories, I think many wavetek models had their piecewise-linear triangle-to-sine shaping network made as a potted module.

David
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Old 29th Mar 2020, 8:22 am   #4
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Default Re: Wavetek model 146

Hi!

The available pdf manual for this is truly gruesome – the parts lists are impossible to read and the circuit–diagrams look like spiders have been dipped in toner–powder and left to scuttle across the pages, and to make it worse, the first part of the main board schematics has been duplicated and all the rest is missing, and some clot has managed to obscure the auxiliary board schematics with a page from the parts list, also unreadable!

However I do have an original on the way which I shall make available when I get a chance to scan it!

I'll be back with repair hints shortly!

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Old 29th Mar 2020, 8:57 am   #5
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Default Re: Wavetek model 146

The best tip I can offer for now is first of all, examine the inside of the unit for obviously burnt or damaged components, make sure all the interconnecting wiring between the rotary switch assemblies and the main PCB(s) is all connected, and in particular, ensure that the leads from the two output amplifier transistors (I think they are Q38 & Q40) are properly connected to the PCB and haven't broken off the devices themselves – these are fitted in bushes fitted to the rear wall of the chassis!

There's no harm in having a prod with the scope on pins 1 to 5 of the A1 triangle–to–sine shaper module – this will give you a rough idea if the waveform is being lost before or after this unit – unfortunately I can't help with more component–level detail than this because, as I said in my previous note, three–quarters of the circuit diagrams in that pdf are missing!

There's far too much of this manual missing for you to be able to work thro' the waveform generator circuits, so if you don't find anything obvious, I'd put the unit on one side for now – there's a better manual coming from me in due course!

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Old 29th Mar 2020, 11:10 am   #6
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Default Re: Wavetek model 146

Quote:
Originally Posted by Chris55000 View Post
Hi!

The available pdf manual for this is truly gruesome

Chris Williams
Are you referring to the manual I linked to in post #2? It runs to 154 pages and I didn't have time to check them all. I noted that it contained fault finding flow charts which I thought might be useful. Personally I'd rather have a poor manual than none at all.
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Old 29th Mar 2020, 11:22 am   #7
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Default Re: Wavetek model 146

Hi!

Yes, and I have been thro' it meticulously and there was no sign of any schematics associated with the A1 module that I could see – I'm fairly sure the original Wavetek 146 main board diagram was at least three, possibly four sheets, and the two there was in the pdf were duplicates of each other!

Unfortunately a lot of people rush thro' scanning/copying these items, understandable if they've had to borrow it from an employer on the q.t., etc., every copy of the Philips PM3305 S.M. I found online had a few circuit and layout diagrams of the input attenuators and the first part of one Y channel and that was as far as it got, so I bought a PM3305 manual myself and uploaded it!

Sorry!

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Old 29th Mar 2020, 12:33 pm   #8
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Default Re: Wavetek model 146

I agree. The manual is very poor, almost unusable.
However, I did a bit more searching and found an American guy that can supply a CD with an original high definition manual for the 146 for $10. Find him on ebay.
I have ordered one from him, and await it's arrival.
I will report back.
John.

Last edited by theredhouseinn; 29th Mar 2020 at 12:34 pm. Reason: typo error
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Old 29th Mar 2020, 3:33 pm   #9
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Default Re: Wavetek model 146

Hi!

Keep us posted!

I don't mind paying for original or well–scanned bookwork, or an original OEM Factory PDF (where not uploaded to free manual repositories)!

Chris Williams
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Old 15th Apr 2020, 3:15 pm   #10
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Default Re: Wavetek model 146

Got the disc from the States.
100% exellent quality service manual in pdf form.
Full spec, block diag., alignment details, fault finding, full cct diag.. etc..
Well worth the £10.32
The ebay id is "artekmedia"
I will report back when I get it back on the bench.
John
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Old 16th Apr 2020, 6:28 pm   #11
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Default Re: Wavetek model 146

Hi!

I've bought a number of Artek Media's products and I've no complaint whatsoever, altho' (personally!) I'd like original manuals containing coloured circuit diagrams or PCB layouts to be scanned in colour of course!

Mauritron's offers are nothing like, verging from the dubious to totally unreadable and useless!

It also seems that I've somehow managed to acquire the original TQ D66 manual aforesaid atrocious quality s.m. vendor vendor used to make the diabolical D65/D66 online one, all the notes, pencil lines, ink blobs, crossings–outs, added bits, etc., etc., are all in exactly the same places!

(How on earth a reasonable original got reduced to that mess online I can only wonder!)

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Old 13th May 2020, 10:41 am   #12
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Default Re: Wavetek model 146

I started on the aux section first as this is the simplest of the two osc's. My expertise is valve and transistor vintage radio, hi fi , and t/v, so test gear repairs are a diversion to a new area. The Wavetek is a very complicated bit of gear.
Basic fault finding techniques came into play, Q3, Q19, Q20, and Q21 all had o/c junctions, obtained replacements online, I had nil stock of these sil pnp types, fitted them, and all waveforms are now present at the o/p skt..
Checking the sine wave on the dist. meter, and it is 4.5%, so still got a small fault yet.
I am going to go through the alignment proceedure as per the manual and see what this throws up.
Then to the main osc. section.
John.
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Old 14th May 2020, 11:51 am   #13
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Default Re: Wavetek model 146

Switched on this morning, no sinewave, sawtooth with clipped tops and bottoms.
The Wavetek block is not converting the sawtooth to sinewave.
Has anyone tried to open up the block?
All the pre-sets were very noisy, so I removed them one by one, and by prising the edge of the adjusting knobs with a fine watchmakers screwdriver I could get enough gap for a squirt of switchcleaner in them. I checked them all on the avo before refitting and all operated smoothly. I will do the same with the pre-sets on the main board.
I checked all of the transistors on the main board except the fet's and 2 of the 2n3640's had o/c b-e junctions, more on the way from the Little Diode company.
This is going to be a long job.
John.
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Old 14th May 2020, 1:43 pm   #14
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Default Re: Wavetek model 146

Sawtooth? Shouldn't the shaping block be converting a triangle to a sine? it's a lot easier.

David
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Old 14th May 2020, 4:22 pm   #15
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Default Re: Wavetek model 146

It is David. To me a triangle is the same as a sawtooth. The block is not converting.
The block is a solid cube of pitch. I have melted most of the pitch off by heating it slowly in a frying pan over a gasburner. It is now soaking in a pot of petrol to clean of the pitch residue.
I can see 2 round 8 leg ic's and a number of resistors and caps on a small pcb.
So far it looks repairable.
John.
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Old 14th May 2020, 11:04 pm   #16
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Default Re: Wavetek model 146

Hi!

Could you post us some high–res pictures of both sides of the PCB when you've got all the pitch and goo off the component bits and PCBs please?

It'll help one of us draw you a circuit diagram of it for reference purposes!

Chris Williams
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Old 15th May 2020, 4:47 am   #17
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Default Re: Wavetek model 146

Those 8-leggers may be nothing more complicated than matched diode arrays.

Connections to the block would give clues. Opamps would need power feeds. Transistor arrays would be another possibility.

Wavetek were ahead of the game with piecewise-linear waveform shaping function generators.

A potential divider chain gives steps of voltage. To each step there is a diode and possibly a resistor in series with each diode. As the signal into an opamp ramps up, successive diodes are turned on, and load the signal, reducing gain from that point upwards. This gives progressively reducing gain. A similar network compresses the negative going half cycle of the input waveform. In this way a triangle wave is converted into an approximation of a sinewave.

This is handy, versatile, and can be swept quickly without amplitude bounces that you get from conventional oscillators. But its achilles' heel is distortion. It cannot compete with a Wien bridge audio oscillator. The shaping networks use matched diodes and the potting is to try to link thing thermally, all in an attempt to keep distortion down. The potting was also for secrecy, but competitors were rich enough to buy a unit and de-pot it pretty quickly.... or X-ray it.

If you tried to make a shaper for a sawtooth into a sine, you could do it, but it would take twice as many shaping sections as one for triangles (each section with the triangle version acts on both the up and down edge) and it would have a monster glitch at the sawtooth flyback edge.

David
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Old 15th May 2020, 3:55 pm   #18
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Default Re: Wavetek model 146

The Wavetek 162 uses discrete components for sine-shaping - just diodes and resistors mounted on the PCB with everything else.

Does make you wonder if - worst-case - you could copy the 162 discrete circuit?

I suspect the 162 is later than the 146. I'm not an expert on their products over the years, but their numbering scheme seems to be sequential, and a quick look at the manuals suggests that's the case.

Love my 162. It's needed a fair few repairs over the years, but it's all discrete and fairly easy to understand. THD isn't brilliant, and because there are so many adjustment points that all interact, it's not the easiest beast to keep in tip-top condition. Despite that, and notwithstanding the arrival of many other skip finds and auction bargains, it's still my go-to waveform generator - probably because it's one of the bits of gear I've had since I was a teenager, and I know it really well. No fans, no software UI to battle with, it just works
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Old 15th May 2020, 6:02 pm   #19
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Default Re: Wavetek model 146

I remember meeting my first Wavetek func gen when I went to uni. They were hellishly impressive at the time. So I pulled the service manual and read it, diagrams and all.

I also read my way through

B&K frequency response setup
Tek spectrum analyser and 7000 scope
Racal RA1217
Brookdeal boxcar detector etc
HP correlator and network analyser.

I had fun!
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Old 20th May 2020, 9:43 am   #20
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Default Re: Wavetek model 146

Quote:
Originally Posted by theredhouseinn View Post
My wavetek 146 has packed up. No o/p from either the main or aux sockets.
All p/s volts are ok.
I have poked around with the scope probe in both sections, but no waveforms can I find.
Does anyone have a cct of this machine?
This is a vintage machine so it can easily be worked on. Discrete components.
In each section there is a block 2" x 2" x 1" high, what are they?
Any info would be appreciated.
john.
I just spotted this thread on the Wavetek. My Wavetek 147 is probably the same sort of vintage as the 146?
It started to give trouble, initially a transistor failed and not long afterwards a second transistor failed. The symptoms were very similar to OC170 failures and I put it down to tin whiskers. I swapped the first for a new device but the second being quite exotic I fixed by applying a reverse bias across it from a current limited power supply. This fused open the short and fixed the problem. Maybe different Wavetek equipments use similarly sourced transistors having the same general manufacturing methods? Both mine are Motorola.
Allan
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