Advance RF Sig Gen Model DIP/2

[Bazz4CQJ]

Can anyone help me out with a manual for this instrument? Mr Google and Mr Bing failed to provide any info at all on this particular model. It covers 2-190MHz and looks very much like model D1D shown here http://www.museum-nt.de/objekte/advance_d1d.html.

Thanks
Barrie

[Bazz4CQJ]

I gather there was a problem with my link; thanks to whoever corrected it.

Having now delved inside the DIP/2, it is very similar to the D1; 5Z4G rectifer, pair of 6J5G's for modulation and an ECC81 RF oscillator. But in the D1 only half the 81 is used, in this model they utilised the other half to act as a crystal calibrator, using a 2MHz xtal in a B9A envelope.

Feeding it with HT from an external PSU wound up on a Variac, the leakage current is a tad high, so I'll do few replacements before powering it under its own steam. For amateur use, these Advance units really are nice generators with effective attenuators and pretty much undetectable RF leakage. And if you are short of an axle stand, they would probably bear the weight of a car on their case .

[Bazz4CQJ]

Almost a year after I acquired it, I've had no success in finding anything out about this particular Advance sig-gen. If anyone can offer any info on this model I would be very grateful.

I can only assume that this model was a special for a particular customer and had only a small production run. Could I have the very last one in existence . With a down-sizing re-location imminent, it competes with my Advance D1D and my Taylor 68 sig-gens for both my affection, and for space on the removals van .

B

[Station X]

Thread reopened at OP's request.

[Bazz4CQJ]

While I'm not very optimistic now, I'm still on the look out for info on this sig gen, which seems to be very obscure. I was checking it out a few days ago and found that the output level is way down. The frequency calibration is fine, the HT is fine and the valve is good, but there's only about 1/10th the output voltage expected.

Just like the D1D version, it is really hard to get at the get access to the oscillator valve base, which is mounted pins down and extremely close to the tuning cap. The resistors I can see have values that don't correspond to the D1D.

Any help appreciated.

B

[Diabolical Artificer]

I've no experience with this model, but have a couple of Advance AF sig gen;s. These have a switched resistor divider including a pot to vary the OP. I'd check those . Have you got a signal on the AF amplifier valve's anode or is the oscillator weak? Are the caps good? What about the VR's, I'd try giving any VR's and inductor's a tweak, that and checking the valve bases.

What is the valve line up on yours? Also as yours is similar in look to the D1D, is the circuit similar? AFAIK Advance used very similar circuits in a lot of their sig gens, tweaking things on newer model's. I'm no expert though. As they're pretty simple devices is it possible to back engineer yours and draw a schematic?

Maybe some pics would help get a few more responses. Good luck, Andy.

[Bazz4CQJ]

The valve line up is; 5Z4G Rectifier valve, 2 x 6J5G AF oscillator, ECC81 VFO / xtal calibrator.

It is the same in the D1D and the DIP/2, the difference is that in the former there is no xtal calibrator, so only one half of the ECC81 is used. Circuit of D1D attached.

When I look at the resistors around the ECC81 valve base, I cannot match the values in the DIP/2 with the D1D circuit. The whole thing is loaded with Hunts' brown moulded mica capacitors, and I know it's the black mouldseal ones that have the bad reputation, but...

As the HT and the ECC81 are good, and there is output on all bands at the right frequency in nice sinewave output, I'm beginning to wonder whether that suggests the problem could be somewhere between the oscillator and the output socket?

B

[Diabolical Artificer]

Could be. It's a case of following the signal to see where it disappears. Is the signal present at V2's grid, is C10 ok? I'm nowhere near as knowledgeable as most forum members,so could be wrong, but it looks like the OP is taken off L1's secondary, so is L1 ok? If there is a signal present at the other two taps of L1 but not at R15, I'd suspect that.

Some of the symbol's are odd, like C18 and 19. Are they capacitance's of a metal shield? We need some input from other chaps here.

Andy.

[Stockden]

If the oscillator is working properly but there's no output at the front panel then the obvious suspect is the output attenuator network (It's quite common for these to have been destroyed by someone inadvertently transmitting into them). I'd follow Andy's suggestion and first check that there's an output on the secondary of L1 and, if there is, follow the path to the output socket until the signal disappears.

C18 & 19 are feed through capacitors and together with L3 form a filter network to reduce RF leakage from the attenuator enclosure.

Hugh

[Diabolical Artificer]

Thanks Hugh, feed through caps, a new one on me.

Andy.

[Bazz4CQJ]

Originally Posted by Stockden

but there's no output at the front panel then the obvious suspect is the output attenuator network (It's quite common for these to have been destroyed by someone inadvertently transmitting into them

As per post #5, there is some RF getting out but well below what it should be. I do believe that these units were largely used by the services, so the possibility that a large burst of RF was accidentally sent inwards, cooking the attenuator, is an interesting possibility.

B

[Diabolical Artificer]

Check the resistor chain is favourite then Bazz. I'd stick my scope probe on L1 to check.

A.

[Bazz4CQJ]

Yep, it's on the "to do list", which should keep me reasonably occupied during the coming week of ..... 'festivities' .

B

[Station X]

Thread reopened at OP's request.

[Bazz4CQJ]

After spending a little over two years trying find a manual for the D1P/2, one has finally emerged. 'Beamcurrent' (Brian) listed a D1P/2 "On offer" which had had been given by a colleague to donate to a BVWS sale last Sunday, and it sold fetching the fine price of £45. It's looking like the buyer was not a member here, but I contacted Brain who was extremely helpful in getting a copy of the manual before it was sold and sending that to me.

I'm just doing a bit of restoration of the circuit diagram and I'll post them presently. Brian's files are large size .png, which I think I will need to convert to load them on the forum (GIF's ?).

Although the "fairly rare" D1P/2 (first made in 1956) looks (physically) almost identical to the much more common D1D, electrically, they are fairly different. The manual says the D1P was made to meet the needs of new "narrow band" receivers. I think that this can be taken to mean AM receivers with improved selectivity, as there's no FM modulator.

The D1D must have been prone to the VFO being pulled when the output voltage / decade switch were used; the D1D takes RF from secondary windings on the inductors in the tank circuit. In the D1P, use is made of the second half of the ECC81 as a cathode follower buffer, and that feeds capacitively from the anode of the VFO, so the rationale for that change is clear. Curiously, while the full output of the D1D is 100mV, the D1P/2 is only 10mV. So having improved stability, they've then tackled improved accuracy by adding in a 2MHz xtal calibrator.

Of course the coverage of the D1D is 10-310MHz and the coverage of the D1P/2 is 2-190MHz, so for most hobbyists, the latter will be preferable.

B

[Bazz4CQJ]

Slightly enhanced circuit diagrams attached

Apart from the comments made in the last post, I find the use of the circuit with the microwave diode downstream of the attenuator curious. They've not applied the modulation to the HT supplying the VFO (as per the Advance D1D) but in to that diode. Also, the crystal calibrator feeds a "proximity connection" (i.e. a dangling wire) in to the screened box with the diode - is that supposed to help produce 2MHz harmonics up to 190MHz?

Any comments appreciated.

Now that I have the circuit for this sig gen I can test it and understand better what results I see. My old notes record that one 743R resistors in the decade box was actually showing 19R and I need to get back to getting it fully working again.

Again, many thanks to Brian for providing the circuit.

B