Marconi 2019 mains transformer - Page 1
Forum section: electronics / repair

author: flamsk
author_rank: Newbie
timestamp: November 13, 2014, 10:09:12 pm
content: Hi, i have a Marconi 2019 signal generator, that blows fuses.. I suspects the mains transformer is faulty. Since i have tested the power supply board right after the mains transformer, using an external supply source. The transformer have 4 seconddary outputs, does any one know which voltages and amp delivery each output should provide? So i can find a replacement?Best regardsHenrik

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 13, 2014, 10:23:24 pm
content: Hi,Check the bridge rectifier(s). I have found shorted bridges in several of these generators.Jay_Diddy_B

author: Fraser
author_rank: Super Contributor
timestamp: November 13, 2014, 10:28:35 pm
content: +1 on the bridge rectifiers. I have also had such a fault on the 2019.While you are inside the unit I suggest you replace the larger power supply capacitors as they age.Aurora

author: flamsk
author_rank: Newbie
timestamp: November 13, 2014, 10:40:58 pm
content: I have tried to disconnect the transformer from the power supply board.. This means that 3 of the 4 secondary outputs are floating, the last one is connected to a bridge rectifier mounted to the case, with the DC side floating. It still blows fuses after a while. I have measured that all diodes inside the bridge should work..

author: Fraser
author_rank: Super Contributor
timestamp: November 13, 2014, 10:45:12 pm
content: The chassis mounted bridge is usually the problem. Mine tested OK on a meter as well. You need to isolate the transformer connections and test the transformer again.Aurora

author: flamsk
author_rank: Newbie
timestamp: November 14, 2014, 05:55:39 pm
content: ok, i disconnected the bridge retrifier and still the fuses blow. nothing but the transformer is connected so it must be faulty.I have tried to measure the resistance of the coils inside the transformer, and some of the coils are less than 0.01 ohm... to must be shorted, I need to find a replacement for it.Do any of you have any specs on the transformer, what are the voltages and max current of each of the 4 secondary output?

author: Simon123
author_rank: Regular Contributor
timestamp: November 14, 2014, 07:28:01 pm
content: Probably something else broke transformer.So check the filter caps and stuff on dc side before you install new one.

author: flamsk
author_rank: Newbie
timestamp: November 14, 2014, 08:35:07 pm
content: The instrument has been sitting in an moist industry environment before i got it. I left it in room temperature for some days before turning it on, but i guess that it was not enough since it broke. I have now removed the transformer and connected external power supplies to the input connectors on the main power supply board in the marconi.And yes it now works!

author: KJDS
author_rank: Super Contributor
timestamp: November 14, 2014, 08:57:31 pm
content: I've got a spares unit 2019 kicking about that has a good power supply. Happy to dig it out and sell the transformer.

author: flamsk
author_rank: Newbie
timestamp: November 14, 2014, 09:05:12 pm
content: Where are you from? And what should it cost?

author: KJDS
author_rank: Super Contributor
timestamp: November 14, 2014, 09:07:27 pm
content: I'm in the UK, £30 plus postage

author: flamsk
author_rank: Newbie
timestamp: November 19, 2014, 04:52:57 pm
content: Hi, how much would it cost in total including shipment to Denmark?/Henrik

author: KJDS
author_rank: Super Contributor
timestamp: November 21, 2014, 02:28:12 pm
content: So I took the unit out of the storage lot and thought I'd take one final look at it before stripping it, but have at last found the fault with it, so now I have a working unit that I'll sell complete.Apologies for taking so long to get back to you, it's been a hectic week.