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Want to buy: HP 3325A attenuator board
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Hello,
I recently bought an HP 3325A which produced no output. I found that the attenuator board was bad. One relay is definitely bad (although the coil resistance measures OK, application of voltage results in nothing happening) and another one seems to be intermittent - it will latch in one position but sometimes may not latch in the other. The relays are the black sealed type soldered into the board, and discontinued: Aromat RG2ET-L2-12V-H10 I'm wondering whether anyone has a parts unit and would like to sell me the attenuator board (if known to be good) - before I devise a make-shift solution? I had the idea of swapping the good relay located in the position that switches from the front to rear output connectors. However it was difficult to remove the failed relay and I am concerned I may damage the good relay if I attempt to remove it, as it has 18 pins. Other than lack of control over the output voltage, the unit seems to be performing well. All functions work including sweep. Thanks, Patrick Wong AK6C |
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An update on my OP. I heard from one member who stated that the attenuator board was a common failure point, hence spare boards were not easily available.
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I tried to find the correct Aromat relay but was unsuccessful in finding a US supplier. A search revealed only one source in India that claimed to have qty 2 of that relay. Rather than send my credit card # overseas, I then decided to buy $6 worth of parts (UPS ground shipping was almost double the parts cost) from Mouser so that I could replace the one failed relay (I decided the other three relays were OK after further testing), a missing 51 ohm resistor, as well as several of the 0.1 uF 50V capacitors which absorb voltage spikes as relay coils are switched. At least two of the capacitors were bad, I was lucky and stumbled across the failed ones (14 total on the board, and they are basically wired in parallel so it is impossible to determine the failed components without removing them one at a time to see whether the remaining capacitors behave correctly or not under an ohmmeter test.) The new relay is an inexpensive low signal 12VDC DPDT latching two coil relay from Omron, DIP configuration with 10 pins. I mounted it dead bug style and ran short leads to the appropriate holes in the PC board. I was concerned that use of an incorrect relay not rated for RF as well as the dead bug installation would result in strange attenuator results. However, when I set the sweep to run from 1 Hz to 20 MHz, sine wave, the signal amplitude on my Tek 2467 varies less than 5% as the unit sweeps from low to high frequencies. I also tested square wave from 1 Hz to 10 MHz and had a similar outcome. This continues to be the case at various tested voltages spanning the full range from a low of 1 mV P2P up to 10V P2P. Hence, a highly successful result at an extremely low out-of-pocket cost. One request: if anyone has a paper copy of the 3325A repair manual, please see whether you have page 5-2 within Section V Adjustments. If you do, I'd really appreciate it if you could scan that page and email to me. I have the pdf copy downloaded from the Agilent manual site, and that particular page is missing. Please send me a private msg if you happen to have that page available. Thanks! Patrick Wong AK6C --- In hp_agilent_equipment@..., "honolulusnowwhite" <patwong3@...> wrote:
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Hi Patrick
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Very common problem on these Synthesizers and therefore very diffcult to find a scraped unit still containing the good relays. You should be able to use the relay which switches to the rear ouptut ok. Let me know if you find an alternative relay part number - I need a couple of thsee. Good Luck Gearoid --- In hp_agilent_equipment@..., "honolulusnowwhite" <patwong3@...> wrote:
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mrcschrdrs
Hi Patrick,
thanks for posting this. My 3325A has the yellow relays directly clipped to the pcb, and the same problem of relays not latching correctly. I discovered the yellow plastic of the relays is cracking, due to age I guess, and so the correct distance to the pcb is not being maintained. Gluing them as best as possible, and with some spacers (scraps of newspaper paper) I managed to get it working again - at least for now. Marc. |
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Hi all,
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My 3325A has the attenuator board marked as "03325-66523 Rev B" which uses 4 yellow "PRINTACT" Latching Relay (12 BW4LD). I think Patrick's attenuator board is the newer "03325-66523 Rev C" which used the relay made by Aromat (Japan). I think Aromat is being merged with the Japanese giant Panasonic. It seems to me "Rev C" is a cost down version because it is not longer having the gold plated PCB. Regards, Dickson Fu VR2WHF P.S. Really wanted to know the model number of the Omron relay used to replace the original Amron relay. --- In hp_agilent_equipment@..., "mrcschrdrs" <mrcschrdrs@...> wrote:
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Hi Dickson,
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The Omron low signal relay that I used to replace the original Aromat relay in the div by 100 position has a manufacturer PN of G6AK-274P-ST-US-DC12 and at Mouser Electronics is priced at $5.43 plus shipping. The new relay is rectangular. I positioned it to minimize the lead length from the relay to the PCB holes that lead to the input RCA jack and to the next relay. I suggest you measure the resistance between the positive voltage wiring harness connectors (pins 1 and 2) and ground. If you do not measure this to be rising to infinity as the capacitors charge up, then you'll know that at least one of the 14 0.1 uF 50V capacitors is bad. A 51 ohm resistor (R1) on the board was missing so I replaced that with a 51 ohm 1W Xicon carbon film resistor. The board has a copper layer serving as a ground plane, and that is a very good heatsink so my 25W soldering pencil did not produce sufficient heat to properly solder the end of the resistor connected to ground. I had to get out my 100W soldering gun to solder that one connection. Using my oscilloscope to monitor RF voltage output and switching between the various functions, I have noticed that *occasionally* the voltage is less than it should be, for example, 2V p-p instead of 3V p-p. I don't think this is a relay problem since the voltage difference is too small to be caused by a relay. Good luck and 73. Patrick Wong AK6C --- In hp_agilent_equipment@..., "Dickson" <dicksonfuhk@...> wrote:
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Hi Dickson,
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Yes, my attenuator board has the Rev C part number as you surmised below. However the exposed circuit traces appear to be gold plated. The serial number of my unit starts with 1748A13xxx, so I think that it was produced fairly early in that product's lifecycle. Patrick Wong AK6C --- In hp_agilent_equipment@..., "Dickson" <dicksonfuhk@...> wrote:
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