Advance E2 O/C Erie

[Avid_Nerdlinger]

Finally got a half-decent signal generator. It appears to have been modified with electrolytics on the attenuated output and AF input. There was no supply to the shielded oscillator circuit and R21 was measuring around 20 megaohms instead of 560 ohms. I don't have any Erie type 9 resistors which are rated at 1/2W so I replaced it with 4 2k2 1/4W 1% metal film resistors in parallel. I'm thinking they should be good enough even though they will be working at 300V.

Now it seems to be working well except for the highest frequency range. I might want to fix that one day but for now I'm nearly ready to align all of my AM radios (parts for TP1B on order). Happy days!

Please advise if you can spot any other mods in the photo.

[Techman]

It's best keeping in mind that if a radio is performing well enough, then messing about with the alignment just for the sake of it is a VERY bad idea. There are delicate slug cores that are easily damaged and it's never a good idea to break and chew up original wax seals just for the sake of twiddling - any good radio engineer will tell you exactly the same.

You also don't know whether your generator is on frequency unless you have a 'calibrated' frequency counter to check it with. Having said all that, the E2 is a very good generator - I myself have had one for many years.

[terrykc]

Originally Posted by Techman

You also don't know whether your generator is on frequency unless you have a 'calibrated' frequency counter to check it with..

I would challenge that statement as you have a number of very accurate frequency sources available to you to check your generator against - they are called radio transmitters!

Loosely couple the generator to a radio and tune the set to a known station. Tune the generator for zero beat and compare the generator reading with the frequency of the transmitter. Repeat this check with stations widely separated in frequency.

I would agree that realignment for the sake of it is not usually a good idea!

As for those resistors 'working at 300V', so what? They won't be dropping 300V will they?

There are maximum working voltages across resistors but these apply to the voltage across the ends of the resistor, not how far above 0V the resistor is!

[Avid_Nerdlinger]

All good advice thanks, I'm less bothered about literal alignment to the frequency on the radio's dial though. Many of my radios do need readjusting but I'm going to try the ones that don't just to see if I can improve the reception of the weak broadcasts we get here, If I can't improve them I'll obviously give up after 1 or 2 or 3... it's just a hobby.

Andrew.

[Skywave]

When any unknown-to-me item of electronics arrives in my workshop, the first thing I do is to give it a mechanical inspection. Then irrespective of what I find, the next step I take is to find a copy of the manual - and read it thoroughly. That acquisition may include the operator's manual and a separate service / maintenance manual.
Next, if any mechanical defects are found, they are put right, especially those that relate to electrical safety: that includes a so-called 'PAT' test. (Example: defective mains lead, and if appropriate, earthing). Next is to assess the performance of the item - and in the case here, in this thread, that will include an assessment of the accuracy of the I.F. amplifier. That 'assessment' will be measurement only: no 'adjusting'! Only after that assessment will I contemplate effecting any repair / maintenance procedures - if, indeed, they appear to be necessary.

Overall, the essential idea is this: assess / examine and only make changes if that assessment indicates work is actually necessary.

Al.

[Skywave]

Originally Posted by Avid_Nerdlinger

Finally got a half-decent signal generator. It appears to have been modified with electrolytics on the attenuated output and AF input.
Now it seems to be working well except for the highest frequency range.

The E2 has an RF output range to about 100 MHz max.. If there are electrolytic capacitors in the RF O/P attenuator, they will need replacing. Electrolytics are not a good idea at high R.F.

Al.