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Hi,

On the Tek 2715 Service manual page 5-16 (adjustment procedures), it says that adjustment C204 is a loop of wire. In my unit the hole was covered up with a metalized sticker but after taking the sticker off, I did no see a metal wire. The voltage at TP300 is stated as being from 8.5 to 9.5v, in my case it measures almost 10.8v. I am wondering if there is a wire for the adjustment (may be broken), but to this I have to remove the RF board which involves some soldering which I would like to avoid.

Has anyone gone through this procedure and can give me some advice?

Alfredo

Hi Alfredo,

1. Which 2715 service manual version are you using? There are at least two manuals, Vol 1 & 2 070-9096-06 (596 pages), and Vol.1 070-9096-06 (682 pages) that I have, Both manuals refer to 2715s with firmware version 12.01.95 and above. After reviewing both manuals, It appears that your page 5-16 adjustment procedure page is the same in both manuals, but I don't know which manual you are using.

2. In both manuals page 5-16 there is a statement: "NOTE. C204 is a loop of wire on later versions of the RF mother board and is adjusted using a nonmetallic tool. Move the loop up or down to vary the tune voltage."

3. Observe the manual states the loop of wire is on later versions, so it may, or may not, be on your RF Mother Board.

4. Is the calibrator signal present, as stated in the manual page 5-16, while you are working on the RF Mother Board section? If not, have you independently confirmed the calibrator signal is present in the 2715 at it's input on the attenuator module (or elsewhere)?

In a bigger picture, what problem does your 2715 have that requires you to work on this section?

Best,
Paul
WB6GHK

Hi Paul,

I have the 070-9096-06 manual.

I hard a good look and found the wire, I think some one has adjusted it before and now its flattened to the PCB.

My instrument does not pass the amplitude normalizations. So I decided to start going through the adjustment procedures. When I measure tp300 which should be between 8.5v and 9.5 it is about 10.1 volts.

I can see the calibrator signal , so I thinks its locked, but reading though the adjustment procedures, I noticed that it keeps mentioning C204, which in my case is a wire, but I cannot adjust it, because its flatted to the PCB.

Regards,

Alfredo

Alfredo,

Hard to troubleshoot long distance, but if you are confident C204 is misadjusted, have you removed the cover and confirmed the wire has been push down to the board?

You should be able to operate the analyzer with the RF Motherboard cover off and then move the wire to see if the tuning voltage changes, but recommend taking a picture first so you can return it to it's original position in case moving the wire makes no change.

Hi Alfredo,

I had a hard time re-aligning my late model 2712 after battery failure and a systemic gain loss after a friend accidently put 50 watts at the input. I thought the input attenuator had failed, but as it turned out 50 watts in and 3.3dB loss were not related and the attenuator is fine.

Best to use latest 2715 manual if your unit has late model PCB. I would start alignment your digital screen setup right first and then use log input. But would suggest checking it first and only adjust as a last resort.

C204 will need raising from PCB, alignment is tricky and fine tuning makes the coupled wires de-shape. However, and in addition while you have the unit open, check your VR transistor Q350. I lost approx 3.3 dB of gain and the device HFE was about one quarter of the stated value, typically a min. HFE of about 100, my device was 11. I replaced the MMBT3904 on A13 assembly. Another member Jaap Rusticus told me He found this issue during his discoveries and suggested I investigate it. This device also gets very hot, I ended up creating a brass standoff on the lid and used a small amount of thermal conductive pad between device and brass post.

I ended up replacing the SMD device with a new 3904 HFE 186 and from that point forward alignment was much easier, I had gained back 4 dB that the normalisation process could do and using the input ref.

Best of luck.

Regards


Gerald

Hi Gerald,

First thanks for the info. It seems I might have the same problem. Since I had noticed that the db values where always off from what I expected.

I will disassemble and check the transistor.

Again, thank you very much for sharing this information, I would have not gotten to this conclusion by myself!

Best regards,

Alfredo

Hi WB6CHK,

I will do that. Thanks for the helping hand.

Best regards,

Alfredo