WTB: Agilent 1GM14201 or 1GM1-4201 microwave amplifier - Page 1
Forum section: electronics / general

author: bernroth
author_rank: Regular Contributor
timestamp: March 18, 2013, 06:17:29 am
content: Hello!I discovered that the Agilent E4432B signal generator (I recently purchased) has a broken output amplifier.With that amp in place, I get a maximum of -60dBm output level, without around 0dBm.The generator should deliver up to 20dBm.Anyone knows where to obtain this part new or used in working condition?I guess this broadband output amp is quite expensive so any hint appreciated where to get it cheaper fromThank you!Best regards,BernhardDB4EC

author: KJDS
author_rank: Super Contributor
timestamp: March 18, 2013, 03:54:09 pm
content: I've just picked up a pile of E4421B sig-gens. One's now got two faults and I'll probably end up using that for spares. I'll have a look when I get chance to see if it has the same output amp.

author: bernroth
author_rank: Regular Contributor
timestamp: March 18, 2013, 05:12:24 pm
content: That would be great, I wait for your reply thenBest regards,Bernhard

author: Fraser
author_rank: Super Contributor
timestamp: March 18, 2013, 05:40:56 pm
content: A quick Google showed that China seems to be the most common source for this chip, either new or used.It might be worth your while emailing some of the campanies. Broadband 20dB 3GHz instrumentation MMICs are not always expensive on the used marketplace. New, they can cost a small fortune as you suggest. I just did an image search on teh part no and a lot appear to be ex equipment so may be affordable.I was going to suggest using one of Mini-Circuits GALi series MMIC's but realise that this would be a very inaccurate substitute for your application. Nice signal Generator by the way.Have you tested it out of circuit to confirm that it is faulty and not being shut down by the signal generator in some sort of self protection mode or an amplifier control failure ?Fraser

author: bernroth
author_rank: Regular Contributor
timestamp: March 18, 2013, 06:12:34 pm
content: I emailed already some companies in China and I wait for their response.Nevertheless I would prefer some local supplierWhen testing the device, I discovered that the maximum output level was raising only to -60dBm when selecting anything between 0 and 20dBm.The generator showed UNLEVEL annunciator on the display which means that AGC (automatic gain control) is unable to regulate the output level to the configured setting.Now I desoldered the amplifier and made a bridge between the input and output. Now the output level can be set up to 0dBm without the UNLEVEL message. Only when I set something greater than 0dBm, the UNLEVEL message appears again.I have not yet found a datasheet for the Agilent amplifier to test it outside the amp.According to my findings, it should amplify the signal by 20dBAs the complete output amplifier module is quite well shielded, it's IMHO impossible to verify all voltages around the device.Tomorrow I will make some photos of the modules, they are very very well built.

author: bernroth
author_rank: Regular Contributor
timestamp: March 19, 2013, 05:32:18 am
content: I just soldered some wires on the supply pins, terminated the input with a 50 ohms resistor, closed the can and checked the voltages with three meters.Attached the results.With the amp back soldered in, same test, the 8.8V drops about by 50mV and +5V by 150mVThere is no difference in the readings when I switch the RF output on/off.The voltages look fine to me, nothing unusual observed.

author: bernroth
author_rank: Regular Contributor
timestamp: March 19, 2013, 03:30:52 pm
content: Thank you!I just have verified the rest of the circuit, no shorts detected. When I put a bridge in place of the amp, I get a constant maximum of 0dBm output level from the preamps, no problems.Maybe KJDS can help me with his E4421 if the output amp is the same. If not, I will have to order a replacement part in Asia

author: KJDS
author_rank: Super Contributor
timestamp: March 19, 2013, 03:44:09 pm
content: I had a look through a service guide last night and I believe the output boards to be the same. I probably won't finish testing the batch of sig-gens that I've bought until the end of next week at the earliest and until then I won't know what parts I have spare. So I may be able to help, but won't know for at least a week and maybe longer.

author: Mosaic
author_rank: Regular Contributor
timestamp: September 03, 2016, 10:05:08 pm
content: Hi, I have to jumper from my the A9 burst mod to the final amp in order to get a leveled ouput to 17dBm. I am not able to trace the signal path fr the RF to the PIN diodes...perhaps bad vias or something.PIN diodes check out ok. Can anyone help with the precise signal path from the mixer IF to its PIN diode and from the burst Mod U180 output to its PIN diode so I can verify please?PIN diode testpointsBelow 250Mhz. Red line = 0V, green = -0.3V, blue = +0.86V and Yell = +1.7V.Above 250Mhz, Red = 1.75V, Green = 0.88V, Blue = -0.2V, Yell = -0.1VI am NOT getting ANY RF at the PIN diodes (but good HI RF at the prior stage) so....I feel it's a PCB issue.

author: nctnico
author_rank: Super Contributor
timestamp: September 03, 2016, 10:43:36 pm
content: Look at this thread:https://www.eevblog.com/forum/repair/e4421b-restauration-project/msg576110/

author: Mosaic
author_rank: Regular Contributor
timestamp: September 04, 2016, 04:42:07 am
content: Interesting but I think u have the sub 250Mhz path wrong.The 1 Ghz LO enters thru U230, amplifies to 13dB as per the level 13 LO requirement of the MCL mixer.https://www.minicircuits.com/pdfs/TUF-2MH+_SPEC.pdfI.F. exits thru the two wound ferrites (pi filter) and enters the PIN network with the DC path thru the 39uH inductor.Kinda hard to track the RF signal exactly as the ohmmeter shows almost the same for the RF & LO to ground. I'll have to desolder the ground to track it properly. Could be a failed microstrip/via situation again.Anyhow, since my last post I have jumpered the input of the burst mod direct to CR202...PIN diode centre pin via a 2200pf COG and I am now getting up to about 15dB leveled >250Mhz so somehow the microstrip/via died inside the PCB. I am going to have to wire a 50 ohm impedance RG316 cable in there and notch the shielding case to take it. The temp. #24awg wire I used causes VSWR issues and leveling comes and goes as I dial up the freq. depending on how the wire is oriented etc.Work remains on the mixer to identify why the IF output is so low, perhaps the output tranny is busted.No specs on that, so I'll have to select one based on the raw mixer IF level as compared to the RF level for similar leveling performance. Gotta check the DC voltages feeding it as well.When I opened the unit I noticed both the mixer pins and the power amp MMIC were resoldered. This means it's possible they were replaced. Something killed the PCB embedded >250Mhz microstrip and possibly the < 250Mhz output amp.Tomorrow I'll spend time tracing the RF of the mixer and checking the conversion loss to determine why my IF is so weak. The 1 Ghz LO is 13dB exactly.