Browning Mark 4 blows 3A fuse

[Deleted]

This is my friend with the Cobra 2000 stuck meters, said his Mark 4 just started blowing fuses after not being used for 5-6 months. It is coming here next. Do the rectifiers short? Are those tube or solid state?

[Sandbagger]

Sept 12, 2009 9:02:50 GMT -5 @vinnies said:

This is my friend with the Cobra 2000 stuck meters, said his Mark 4 just started blowing fuses after not being used for 5-6 months. It is coming here next. Do the rectifiers short? Are those tube or solid state?

Yes, rectifiers short, and yes the MK IV is still tube. Check for shorted filter caps as well.

[mark4]

They sure do!
And anyone of them could have shorted.
I have seen the -45v supply with a shorted bridge.
This tends to be the least problem bridge in that radio.
Not much of a current draw there at all.
The standard here is they all get changed and every last electrolytic capacitor also.

[Deleted]

Any specific size bridge?

[mark4]

the -45v you need nothing more than a 1amp bridge.
the high voltage bridge I would use a 2amp.
And the 9V supply you need a 4amp.
Sorry, no time to look up the numbers right now.

[Deleted]

Thanks for the size. Don't worry about the numbers. I just needed the sizes. This is a not a 4A. What was the difference between a 4 and 4A?

[Deleted]

2 questions:

1. The bridges look cooked. I have a cross for the PD1011. It is a RS401L. Does anyone have the cross for the PD1560?

2. Does anyone have a componet identification layout of the radio? There is a manual on CB Tricks, but no parts layout page.

[mark4]

Order a 2 amp bridge 1000V
Mouser part# 583-RS207L

[Deleted]

Great job! Thanks!

[mark4]

Glad I could help.
You asked what was the difference between a 4 and a 4A.
The only difference to speak of is the readout and PLL boards.
The 4A is a more advanced better design. The 4's were trouble.
But I fix them all the time. And mine are very reliable I use them almost everyday. Allot of upgrading was done. And the 4's convert wonderfully with a custom programmed PROM.

[Deleted]

Thanks. I ordered the bridges, caps, and some metal oxide power resistors. Then I found out that he is dumping it after I fix it. Go figure.

[Sandbagger]

Sept 27, 2009 17:15:14 GMT -5 @vinnies said:

Thanks. I ordered the bridges, caps, and some metal oxide power resistors. Then I found out that he is dumping it after I fix it. Go figure.

Then charge him a good fair price for fixing it. I don't mind helping out a friend who wants to restore an old classic for his own use, but it sort of tweaks me to have a friend take advantage of my knowledge to restore something so they can dump it for maximum profit.

[Deleted]

He gave me the GE Superbase. The work involved isn't that hard. But after this radio, I am restoring a Johnson Viking II for myself. I need about another $500 for a Yaesu FT-950 with a Heil GM-5. I had to sell my Icom 746, because their support sucks.

Funny, but one thing I notice from my friends is they try and buy the latest and great thing. The guy who's Colt I repaired, went from a Browning III, to Cobra 2000, dumped the Browning for a Tram 201A, dumped the Tram and a Kenwood TS-850 for a Icom 746pro. He now only has the Icom and Cobra 2000 left. All this since last winter. I don't get it.

[2600]

There's a name for that syndrome.

Called "The Grass Is Always Greener", pretty sure.

73

[Sandbagger]

Sept 27, 2009 21:26:49 GMT -5 @vinnies said:

Funny, but one thing I notice from my friends is they try and buy the latest and great thing. The guy who's Colt I repaired, went from a Browning III, to Cobra 2000, dumped the Browning for a Tram 201A, dumped the Tram and a Kenwood TS-850 for a Icom 746pro. He now only has the Icom and Cobra 2000 left. All this since last winter. I don't get it.

I've known a few guys like that over the years. They never kept any radio for long, and were always horsetrading or buying and selling. I'm not sure if it's simply a case of quickly getting tired of one rig, and just wanting something different, or if it's one of those itches that can't be scratched, like someone looking for the perfect radio and never quite being satisfied.

[Deleted]

One thing that keeps them selling, is if they here a rig that sounds great onthe air. He seems to have to have that. He has got some steup that he purchasec from someone. It used the Icom 746 as a receiver, and a Cobra 29 as a transmitter. It switches over using a relay. He heard it on the air, and had to have it. All for the CB band, only. Nuts!

I still have to find a CB with the receive of my TRC-455. I must have paid about $60 total in purchased/repair costs.

[Deleted]

OK, this is a stupid question. I removed both bottom and top covers. Which goes to which? I have a louvered bottom and a bottom with many holes. Are the tops interchangeable?

[2600]

The perforated bottom has a lower resistance to airflow than the louvered cover. It goes on the receiver, to accommodate the higher level of heat produced in that side of the radio.

And I've seen more than a few Mark IVs with the perfed bottom on both units. The transmitter runs pretty hot if it has the stock setup inside it.

The top covers should both have louvers on the sides as well as the top. More than once I have seen a Mark IV with Mark III covers. Probably swapped by an owner who fancied the better airflow for his Mark III.

73

[Deleted]

OK good and bad news.

Good news first. I recapped the radio and replace both the bridge rectifiers. There was a third set of 4 individual rectifier diodes that I did not replace. The fuses don't blow anymore, and none of the caps blew up, meaning I put them in the right way. I have receive.

Now the bad news. No transmit. No LEDs light up on either the TX channel display, or the band modes onthe RX. Relay is not clicking when I key the mic.

I did not measure the voltages at the molex connector, because I was done for the night.

Anywhere I should start looking? Looks like I am missing a supply voltage. Should I have replaced those 4 individual rectifer diodes?

[rjordan]

Your luck is like mine it would seem ;D

I'm not certain they're bad, but yes, most likely the 4 individual rectifiers you mention are part of the circuit you appear to be having trouble with.

Based upon your description of the problem, it appears you are missing the raw 11V Supply voltage generated by a supply located inside the receiver. I say "raw" - it is not a regulated voltage, and will not be exactly 11 volts.

On the receiver side, it feeds the 6 front panel LED's. This voltage is also applied to a switching circuit used to select between the two First Local Oscillator crystals which determine the receive range - either the CB1 or CB2 band.

On the transmitter side, this 11 volts feeds the two 7805 IC voltage regulators. These regulators generated the proper voltages for all of the TTL logic chips inside the transmitter, as well as the voltage for the channel display LEDs.

Now, for a few suggestions on what to look for....

Inside your receiver, I believe you'll notice two green/yellow wires that are coming out of the power transformer and go to the section where the four individual diodes are located. There will also be a filter cap - possibly two filter caps - rated for around 16 volts (no less). More on what/why below. Just to make absolutely certain you don't get any false readings, I would lift one end on each of the four diodes and test them individually. While working in that area, look for any missing or poor connections as well. You can set your VOM for AC voltage and check that you have around 7 volts or so across the two green/yellow leads.

Now, for the "why" I mentioned above.

The original Mark IV's used a PD1011 full wave bridge rectifier for the raw 11V supply. That was then changed to a PD1560 Full Wave bridge rectifier. Engineering change order 78008 issued 2/2/1978 instructed that all radios built after arrival of new parts were to use 4 individual PD4722 diodes arranged as a full wave bridge. These are 3amp at 400 volt rectifier diodes. The change was to prevent bridge rectifier failures. I use 1N5408 diodes for replacement purposes. The 5408 is a 1kV PIV rated diode, so I just stock it as a "universal" replacement for any 3 amp service requirements. Mouser's part number is 821-1N5408. There were also two 2200uF at 16VDC filter caps that were changed to one 4700uF at 16VDC in that supply as well... make certain it's not shorted or has low resistance.

One odd thing about your situation. You mention a "molex" plug, so the radio you're working on is prior to the change over to the cinch-jones connector. Most likely, your radio was built prior to this change order. The repair order for the power supply upgrade I mentioned above specified that this change was also to be done to repairs as well. I would be surprised if your radio was upgraded by the factory with the 4 individual diodes however, as there was also a repair order for replacing the molex connector with a cinch jones connector while units were in for repair.

Your individual diodes were most likely installed "in the field."

BTW, did the manual help any on your Wavetek 3000?

[Deleted]

Rjordan. Thanks so much for the info! You might be right on the plug. I will check the diodes tonight. I did replace those 2 caps with two 2200uF. What that OK? I figured there wasn't much difference between that and 4700uf.

The Wavetek manual unfortunately had the same power supply diagrams that my manual had. My unit seemd to have a completely different supply, regulators, filters, and all. There are not even close. On a good note, I was able to disassemble one of the cans, and found that they use very common RS4558 dual op amp chips. Basically dual 741. So, I am going to order about 25 of these, as they are all over the unit. Also, they are socketed, making replacing them a breeze. I will follow up. Keep on eye on this thread. I need to get this off my bench so I can start a restore on a Johnson Viking II.

[Deleted]

More good news, less bad news.

Good news. You nailed it on the head. One of the legs from the diode came off from the terminal strip, when I resoldered the caps. The diode legs were not even inside the terminal strip. LEDs' are back, and so is transmit.

Now the less bad news. The TX LED channel display is stuck at 01. It will not move up or down. This seems to be the only remaining problem.

[rjordan]

Oct 2, 2009 19:43:27 GMT -5 @vinnies said:

More good news, less bad news.

I really like your outlook on things

You're fine staying with the original setup of 2 2200uf caps versus the one 4700uF - just as long as each of their working voltages is 16VDC or higher. You're not dealing with an application where dissimilar ESR values are going to give you problems here. If you have a 4700uF, you will save some room in the chassis - that's up to you.

Now, on to the less bad news. Can you provide some additional information please.

Are you transmitting on channel one - on frequency (easiest to test on AM with no modulation)? Is the low limit LED lit? Do you see any blinking or any apparent brightness change in either the low limit LED (if lit), or any of the segments in the channel display window when you turn the channel selector knob clockwise and hold it for 8 or 9 seconds? Same question when you turn the channel selector knob counterclockwise. Please tell me what the display does when you rotate the TEST switch to the LED position, and what it does when you rotate the TEST switch to the RESET position.

Also, rotate your Scan Rate pot to some different positions and see if you can change channels with that pot in some other positions than it is in at the present time.

Also, take a peak at the wires going to the scan pot, the reset switch, and the display logic boards - looking for a broken or loose wire in those areas. One other thing you can try..... with power completely off, you can remove the top two screws on the transmitter's front panel that hold the display board in place. Gently push the display board back and press on all of the IC's to make certain they're firmly seated in their sockets. If you have a light touch, you can also gently rock them a little in their sockets to "wipe" their leads. Do the same thing on the "piggy-back" board sitting behind the front board where the 2 7-segment LED's are located. If you do this take note!!!!! There is a small washer acting as a spacer that goes between the lip of the front panel and each of the "L" brackets attached to the display board.

Assembly is like this

Top of front panel: Screw -> / front panel lip / washer / L bracket

Each of the two mounting screws will have a little washer (or should have at least)

Those darn little washers (which they are using as spacers) love to fall out and into the hardest places to retrieve. They especially like to fall across a high voltage point and ground in order to test your fusing capacity ;D

Let me look for any other information I might have on your Wavetek. If you were to guess, would you say your power supply is newer or older than the ones shown in the manuals you have?

Rick

[Deleted]

I finally got back to this after 2 weeks of finishing off my garage, which looks like a garage again!

I did verify that the unit is transmitting on ch 1, as the stuck display indicates. I did not check the 555 pulses on a scope yet. I might just replace it anyway. I will get to play with it more this week.

[rjordan]

Oct 18, 2009 21:18:46 GMT -5 @vinnies said:

I finally got back to this after 2 weeks of finishing off my garage, which looks like a garage again!

Any chance you'd like take a try on mine? I'm going to have to do something soon, or else I'm going to be outside scraping ice on HER car very soon LOL!

[Deleted]

This guy called me up and ask me where I was with the Mark IV, Because he said he wanted me to take a look at his Tram. This is after I fixed his Cobra 2000. He had given me a GE Superbase for exchange of working on this equipment.

I fixed his Cobra 2000.
I got his Mark IV working, except it was stuck on Channel 1 transmit.
He wanted me to take a look at the Tram.
The VFO on the Icom 746pro was getting stiff.
He wanted me to look his Yaesu amp which was not putting out.

I called him up the other night, and said to come get the Mark IV, and come and take back the GE Superbase, because I wasn't working on any more of his radios. I am done.

I cannot believe people. I tried to make a fair deal to work on his rigs in exchange for a $250 radio, except he failed to tell me that his entire collection needed work. I have never seen an operator that had ever radios that he owns, have some sort of problem.

[Sandbagger]

Nov 14, 2009 21:36:45 GMT -5 @vinnies said:

This guy called me up and ask me where I was with the Mark IV, Because he said he wanted me to take a look at his Tram. This is after I fixed his Cobra 2000. He had given me a GE Superbase for exchange of working on this equipment.

I fixed his Cobra 2000.
I got his Mark IV working, except it was stuck on Channel 1 transmit.
He wanted me to take a look at the Tram.
The VFO on the Icom 746pro was getting stiff.
He wanted me to look his Yaesu amp which was not putting out.

I called him up the other night, and said to come get the Mark IV, and come and take back the GE Superbase, because I wasn't working on any more of his radios. I am done.

I cannot believe people. I tried to make a fair deal to work on his rigs in exchange for a $250 radio, except he failed to tell me that his entire collection needed work. I have never seen an operator that had ever radios that he owns, have some sort of problem.

Welcome to the world of the neighborhood CB technician. I used to know people like that back in the day when I used to fix stuff for the locals. I guess they figured that it was a heck of a lot cheaper for me to do it for parts plus $20, or in trade for some other piece of gear, than it was to take it to a "legitimate" shop, that would charge half the value of the radio just to replace a blown final or similar. I once had a "friendship" go out the window over my sudden unavailability to work on his radios at the drop of a hat. Some people are just users and they'll take advantage of your good nature.......

[Deleted]

Clearly, when I made the deal, he worded it in a way where he said that if he had problems, I would look at it for him. He didn't mention that he had currently problems with every rig. I did a little asking around about him, and found out he would only buy near mint rigs, and then immediately send them out to Barkett and so forth, for overhaul. He would spend outrageous money doing this. That person also told me that he had some kind of quirk that he always needed to have his radios serviced as a feeling of security.

What set me over the top is that he wanted to dump the Mark IV, and then and the Tram for me so he could dump that, too. That was it. The mutual friend thought I was nuts because of all the work I did, and shouldn't have given back the Superbase. I looked at it another way. I cut my losses early, and opened up time to work on my own rigs, which have taken a back seat to everyone else's.

[wd8nia]

Sounds like y'all are talking about me. Before I croak, I want to try out every rig I can, I'm kind of limitied on radio funds, so I have to horsetrade to switch rigs. Also, I've got a lot of work backed up.

I pulled my FT-757GXII station out of storage (been packed up in the shed for about 10 years), set it all up, hit the power button....dead as a doornail. The transceiver was completely gone through a few months before storage, and it worked perfectly when I boxed it up.

My Azden PCS-4000....neat little rig, but pretty much same story. Fired it up....zero modulation.

I need my Galaxy DX 2517 re-crystalled and aligned for 10 Meters.

My Tram D60 now suffers from low modulation and I need the clarifier reworked because of the upper channel mod syndrome.

My D201 works just fine....killer rig....but it's time it was gone through.

That's not the tip of the iceberg....it's the ripple in the water where the tip's about to punch through the surface.

I've pretty much always got so much radio crap going on, it's a wonder how I can manage to keep up with the chores around the homestead and hold down a full time job on the side.

[Deleted]

But I have a full time job (same employer for last 15 years), and a 3 year old daughter.

That guy thought I come home, and have nothing to do but work on radios. Even though I reiterated that I am not a tech or a CB shop, and that I do this without time constraints, and whenever I can get to them. They cannot seem to comprehend that. They think I do this full time.

Don't matter. It's over. I have 3 rigs to work one now, all mine and all projects.